by definition a restrictive clause is what?

Question

a) conveys confidential information.
b) is essential to understanding the sentence.
c) provides extra, optional information
d) follows a colon.

Answer 1

"C"

A subordinate clause that limits or restricts the meaning of the noun phrase it modifies.
http://wordnet.princeton.edu/perl/webwn

In syntax, the concept of "restrictiveness" applies to a variety of syntactical constructions. Language learners most commonly encounter it in the context of relative clauses, where it is particularly problematic for learners of English, but linguists use the concept in a broader range of contexts.
http://en.wikipedia.org/wiki/Restrictive_clause

Answer 2

Looks like option D, but this sure is an odd question! Hope you're having fun with it!

Answer 3

b