For the answer to the question above, I believe it is various forms of be.
The most common linking verbs are, am, is, are, was, were, being, and been, so the correct answer is the third choice among the given questions.
1. Busiest
2. Close. Closer
3. Good. Better
4. Noisier.
5. Safest. Most dangerous
The correct answer is B. Comparative form of adjectives compares two things or people. They are used in sentences where two nouns are are compared. For instance, "My house is smaller than hers.", "Your dog runs faster than my dog."
An adjective clause is a dependent clause that, like adjective which modifies a noun or pronoun. Adjective clauses begin with words such as that, when ,where, who, whom, which, and why...... hope that helps!!!