In Engish lanuage, verbs have different forms in different situations (mainly depends on the time) and should be paid carefully attention. The different forms are called Verb Tenses. Verb tenses can be described in four different categrates. They are Simple Tenses, Progressive Tenses, Perfect Tenses and Perfect Progressive Tenses. It's absurd to talk about grammer without examples, so let's have a look at the following sentenses:
I am a couch potato.
I was a couch potato.
I'm going to become a couch potato. (too bad)
The three sentenses are all in Simple Tenses. The first one is in "Simple Present" tense. It can be used to describe the situation at present, like i am now a cough potato. Or it can also express events or situations that exits always, habitually. For example, "The earth is one of the planets of the Sun." The second one is in "Simple Past" tense. It indicate that what the sentence is descrbing happened and ended in the past. Therefore in the past I was fat but now no more. The third one is in "Simple Future", which indicates what is going to happen in the future. Thus it is quite bad for me to become a cough potato if I continue eating so much.
With the knowledge of Simple Tenses, lets move on to Progressive Tenses. Its form is "be + -ing(present participle)". For instance:
I am writing portfolio 2 right now.
I was writing portfolio 2 at this time yesterday.
I will be writing portfolio 3 tomorrow morning.
These sentenses are in "Present Progressive" tense, "Past Prograssive" tense, and "Future Progressive" tense respectively. They all describe my progress of writing portfolio. The difference is that in the first sentense, I am doing it at present; in the second one the progress is in the past; in the third one the progress is to happen in the future.
For the Perfect Tense, it also has three types, "Present Perfect", "Past Perfect", and "Future Perfect". The Perfect Tenses give the idea that one thing happens before another time or event. For instance:
I have been a couch potato for a year already.
I had been a couch potato last year but now I am slim.
I will already have been a bigger couch potato if I didn't insist on jogging everyday since last year.
Last but not least, for the Perfect Progressive Tenses, the form is "have+ been + -ing", as the sentenses below:
I have been studying since morning.
I had been studying before friends called me to have lunch.
I will have been studying for the whole morning by lunch time.
Through the examples we can see that Perfect Progressive tense gives the idea that one event is in progress immediately before, up to, until another time or event. The tenses are uesd to describe the duration of the first event. In the first sentense, I have been in progress from moring up to present. In the second one the progress was before lunch time. In the third one, until lunch time I would have been in the progress for the whole morning.
In the following passage from Alex Haley's Roots, some of the verbs have been deliberately omitted. Supply the appropriate tense for each missing verb, the plain form of which is given in parentheses.
In Banjuh, the capital of Gambia, I met with a group of Gambians. They __(tell)___ me how for centuries the history of Africa has been preserved. In the older villages of the back country, there are old men called griots, who __(be)__ in effect living archives. Such men ___(memorize)_____ and, on special occasions, _(recite)____ the cumulative histories of clans or families or villages as those histories __(have)____ long been told. Since my forefather _(have)___ said his name was Kin-tay (properly spelled Kinte), and since the Kinte clan __(be)___ known in Gambia, the group of Gambians would see what they could do to help me. I was back in New York when a registered letter __(arrive)___ from Gambia.
Word ____(have)___ been passed in the back country, and a griot of the Kinte clan _(have)____ , indeed, been found. His name, the letter said, __(be)__ Kebba Kanga Fofana. I __(return)___ to Gambia and __(organize)_____ a safari to locate him.
Answers: told; are; memorize; recite; have; had; was; arrived; had; had; was; returned; organised.
Basically this exercise is testing on Past Tense. In order to get correct answers, to read carefully between the upper and lower sentenses is very important and effective. If the whole sentense is in Past Tense, like the first sentense, then the verb should be in Past Tense as well.
I am still looking for some more difficult exercises which test all the verb tenses. :)
