"Why does the author say "It's enough to make you want to bury your head"?"

Without context, it is slightly difficult to tell what the correct answer is, but I am fairly certain that the answer is "The great number of problems can make you want to pretend they do not exist."

Explanation:

If you bury your head, it means to ignore unpleasant realities, so the last answer choice seems the wisest.

- "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)."