Chapter 10: The Four Main Forms (来源：英语麦当劳－英语快餐EnglishCN.com)

Verbs are one of the essential ingredients in the creation of sentences.
Verbs tell the reader when something occurs through the use of tense. Tense is
time. Verbs tell the reader whether the action is happening now, in the past,
or in the future. Verbs have four main forms and it is these forms used alone
or in combination with helping verbs that create the tenses.

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The four main forms are the present form, the past form, the present
participle, and the past participle.

In addition to having four forms, verbs also come in two types-regular and
irregular. Regular verbs use the same pattern to create the main verb forms;
irregular verbs do not use the same pattern. Three of the most common verbs in
English are irregular verbs and need special consideration. Those verbs are
be, have, and do. Good writing requires that the writer have mastery of verbs
and the main forms of both regular and irregular verbs.

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Chapter 11: More on Verb Tenses (来源：英语论坛 http://bbs.englishcn.com)

You have already studied in Chapter Ten the four main verb forms. These
verb forms are combined with helping verbs to create tenses other than the
simple present and simple past tenses. Some tenses describe the continuation
of action from the past to the present or the present in to the future. In
addition, some tenses describe more than one action being completed in the
past, but at different times. These are the progressive and perfect tenses. (来源：英语麦当劳－英语杂志 EnglishCN.com)

The progressive tense is created using a form of the verb be with the
present participle of the main verb. The perfect tenses are created by
combining a form of the helping verb have with the past participle. It is
important not to confuse these tenses with the simple present and simple past
tenses. An easy way to separate them is to remember that both the progressive
tense and the perfect tenses use helping verbs. Simple tenses do not use a
helping verb.

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It is important when you work with the past participle to put the -d ending
on the participle particularly for the verbs use and suppose. In addition,
make certain that you do not substitute the preposition of for the verb have
in phrases like could have, would have and should have. (来源：英语资料下载 http://download.englishcn.com)

Chapter 12: Verbs: Consistency and Voice

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Once you have decided whether to write in the present tense or the past
tense, you must remain consistent. You cannot shift tenses in the middle of a
sentence or the middle of a paragraph unless there is a reason within the
context of the writing to make a change in time. In other words, you can't go
from the past to the present and back to the past if all the events you are
describing occurred in the past. You must remember when you are editing to check
the tenses to be sure that you have been consistent with the choices you've
made. Correcting shifts is easy. Simply choose one of the tenses and make
everything with in the sentence that tense.

Voice describes the subject of the sentence. When the subject of the sentence
does the action of the sentence, it is considered active. When the subject of
the sentence does not do the action with in the sentence, the subject is
considered passive. Passive voice is wordier and weaker than active voice so you
should avoid using it whenever possible

Chapter 13: Making Subjects and Verbs Agree

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Subjects and verbs have to agree with each other in number. It is not
acceptable to mix a plural subject with a singular verb or vice versa. Singular
subjects must be paired with singular verbs and plural subjects must be paired
with plural verb. It is important to be certain that you are selecting the
correct word in the sentence as the subject. Whenever you are dealing with
sentences that have prepositional phrases, eliminate the phrases before choosing
the subject. Sentences that have inverted word order or begin with here or there
often have the subject following the verb rather than in front of the verb. Once
again look carefully before selecting the subject to agree with the verb.

In addition to these problems, compound subjects, indefinite pronouns, and
collective nouns all present possible agreement problems. Compound subjects