Subject verb Agreement

Basic Rule

The basic rule states that a singular subject takes a singular verb, while a plural subject takes a plural verb.
NOTE: The trick is in knowing whether the subject is singular or plural. The next trick is recognizing a singular or plural verb.
Hint: Verbs do not form their plurals by adding an s as nouns do. In order to determine which verb is singular and which one is plural, think of which verb you would use with he or she and which verb you would use with they.
Example:
talks, talk
Which one is the singular form?
Which word would you use with he?
We say, "He talks." Therefore, talks is singular.
We say, "They talk." Therefore, talk is plural.


http://grammar.ccc.commnet.edu/grammar/cgi-shl/quiz.pl/sv_agr_quiz.htm

http://grammar.ccc.commnet.edu/grammar/cgi-shl/quiz.pl/agreement_add1.htm

http://www.cityu.edu.hk/elc/quiz/subverb1.htm

http://www.towson.edu/ows/exercisesub-verb2.htm

http://xnet.rrc.mb.ca/leshanson/Hot_Potato/SV_Agreement_6.htm

http://www.wisc-online.com/Objects/ViewObject.aspx?ID=WCN3302

http://a4esl.org/q/h/vm/svagr.html

http://www.eslbee.com/sv.htm

Main and Helping Verbs

Main Verbs and Helping Verbs

A verb may be more than one word. The main verb is the most important verb. The helping verb comes before it.

Some Common Helping Verbs

am                       was                           has

is                        were                          have

are                       will                                had

The main verbs below are in bold print. Helping verbs are in italics.
Alfredo is training for the Olympics.
 
He has run five miles each day.
 
His coach will help him next week.

http://www.ucl.ac.uk/internet-grammar/verbs/ex4.htm

http://www.softschools.com/quizzes/grammar/helping_verbs/quiz520.html