Verb Tenses
It is a common sense that no one wants to read an essay filled with mistakes, especially grammar mistakes. Thus students should focus on their grammar mistakes while writing and correct them carefully after ending. The most serious grammar problem for me is the Verb Tenses. There are mainly two reasons for making mistakes.
One is the habit, which is common for basic verb tenses. For example: the simple future, the simple present and the simple past. Students are familiar with these tenses. However, when they are writing an essay, it is hard for them to focus on the verb tenses all the time, thus mistakes coming about. For this situation, students should care more about the basic Tenses and learn to check them after finishing an essay.
Another reason is the unclearly about the tenses. There are some advanced verb tenses that students are not familiar with. For example: the progressive, the perfect, and the perfect progressive. The progressive tenses give the idea that an action is in progress during a particular time and these tenses tells that an action begins before, is in progress during, and continues after another time or action. The perfect tenses give the idea that one thing happens before another time or event. The perfect progressive tenses give the idea that one event is in progress immediately before, up to, until another time or event. These tenses are used to express the duration of the first event. For such verb tenses, students should analyze them carefully and read the paragraph carefully. One basic rule is the correspondence of the context.
Knowing the rules of verb tense is far from enough. Students should do more exercises to strength their memory and improve their analyzing ability. Below is an relevant exercise.
Exercises
Of all man’s natural enemies, the one which has caused him more trouble than any other must be the common rat. For centuries, man (1) ____________ (try), in vain, to solve the problem of rats. The ancient Egyptians (2) ___________ (be) probably the first people to try to get rid of them with poison, and this method (3) _____________ (still be used) today. This says a great deal about how effective this method (4) _____________ (be). We have set innumerable and ingenious traps, from simple wires to complicated machines which drowned the rats in beer! We (5) ___________ (use) gas, water and fire. We have tried to electrocute them and to infect them with specially developed germs. We've even tried to breed super‑cats to kill them. However, we are still losing the battle.
One of the first records we have of the problem of rats was in 1347 when some Italian ships (6) ___________ (carry) rats from the Black Sea back to Italy. Soon, the citizens (7) _____________ (complain) of painful dark marks on their skin. Soon after that, they were dead. This was the beginning of the 'Black Death' which killed 25 million people in only three years. For centuries, the same disease, also called the plague, would wipe out thousands of people from time to time and in different places. Thankfully, this is a problem that man (8) ________________ (almost overcome). Plague today (9) ___________ (be) not the threat it used to be. Only a few countries in the world (10) ___________ (still have) an occasional death caused by the plague. However, the rat is still alive and healthy.
Although the problem of plague has been contained, the rat is still man’s number one enemy. This year, in the United States alone, rats will bite thousands of humans, causing disease, despair and terror. They (11) ___________ (destroy) well over a billion dollars worth of property. In a world constantly suffering from famine, rats will destroy approximately a fifth of all food crops planted. In India alone, they (12) ___________ (deprive) hungry people of enough grain to fill a train more than 2,000 kilometres long. In all of Asia, rats (13) ___________ (eat) 48 million tons of rice a year, enough food to feed a quarter of a billion people. Around the world, rats will spread at least 20 kinds of disease, and in several tropical countries their population will suddenly explode and completely destroy the land.
'When we speak of rats,' (14) ___________ (explain) one leading scientist, 'we are speaking of the most numerous and successful mammal on earth, perhaps including man! When we talk about rat control, we're talking about human survival.'
So why can't man, with all his scientific knowledge, manage to overcome a mere animal like the rat? The answer is simply that the rat isn't a 'mere' animal ‑ it (15) ___________ (be) a very special kind of animal. An average rat can: wriggle through a hole no larger than a S$1 coin; climb a brick wall as if it (16) ___________ (climb) steps; swim for one kilometre and then tread water for three days; chew through lead pipes and metal bars with teeth that can exert an unbelievable 1,691 kilograms per square centimetre; happily leave a building by being flushed down the toilet, and then return the same way; jump from a fifth storey window and run away unharmed; and last but certainly not least, multiply so rapidly that a single pair could have 15,000 babies in one year!!
Perhaps the best example of how 'special' these creatures (17) _________ (be) is found on the island of Engebi, in the Western Pacific. For many years, the United States tested its nuclear weapons on this island. The rat was “completely” destroyed by repeated nuclear explosions. A few years after the explosions (18) ___________ (stop), scientists visited the island and found it was alive with rats. The rats were not injured or weakened in any way. On the contrary, their life spans were longer and, if anything, they were larger and stronger than other rats. It (19) ___________ (seem) that the most deadly weapon that people can create actually (20) ___________ (improve) the health of our oldest enemy!
In addition to all these physical qualities, we also have the problem that rats are rather good at (21) ___________ (not get caught). They seem to have an almost supernatural ability to sense when food (22) ___________ (be poisoned) (even as little as one part in a million) and a suspicious rat will starve before it (23) ___________ (eat) poisoned food. They also seem to be able to recognize a trap with no real difficulty.
To overcome these abilities of the rat, we now use a huge variety of weapons, both sophisticated and simple. We (24) ___________ (experiment) with chemicals, radiation, high‑frequency sound, and even super‑glue! There is now a machine on the market which (25) ___________ (claim) to grab the rat, electrocute it and neatly seal it in a plastic bag. However, the simplest method (26) _________ (be) probably also the oldest, a strong wooden club. It (27) __________ (prove) very effective in Bombay, India. Every night, the rat‑catchers take to the streets armed with such a club. They find a rat with the beam of their torch, crack it over the head, pick it up with their toes and drop it into a sack. In total, they (28) __________ (kill) 4,000 a night, which (29) ____________ (be) a mere drop in the ocean. One thing (30) _________ (look) certain, we had better find a way to defeat these small brown creatures soon, or it may be too late. In the age‑old battle between rats and people, the rats are perhaps beginning to win!
Key to the intermediate level exercises
(1) has been trying, (2) were, (3) is still being used, (4) has been, (5) have used, (6) carried, (7) were complaining (or complained), (8) has almost overcome, (9) is, (10) still have, (11) will destroy, (12) will deprive, (13) eat, (14) explained, (15) is, (16) were climbing, (17) are, (18) had stopped (or stopped), (19) seems, (20) improves, (21) not getting caught, (22) has been poisoned, (23) eats, (24) are experimenting, (25) claims, (26) is, (27) has proved (proves), (28) kill, (29) is, (30) looks.
(slightly adapted from an extract in Burns, J. & Smallwood, I. (1990). Impact 4, McMillan)
