Which of the following statements about irregular verbs is correct?
a. to form the past tense, an irregular verb needs a –d or –ed.
b. the rules about irregular verbs are simple and easy to learn.
c. to change tenses, an irregular verb has to change its spelling.
d. each irregular verb is preceded by the word "to."

1.d

1.e                                  

2.c

3.c

- "a nonrestrictive clause functions as a modifier to a noun (that is an object, person or concept). these clauses can be described by the following three options: it is set off by comas, it contains a subject and a verbs and it adds nonessential information to the sentence.

for example, in "here is bill gates, who confounded microsoft software company" we can identify "who confounded microsoft software company" as a nonrestrictive clause modifying the noun bill gates. this clause can be describes as a nonrestrictive clause because it is separated by a comma, it adds nonessential information to identify who bill gates is and it must contain both a subject (who) and a verb (confounded)."