The board of directors . . . . . . . . anxious.

A. are

B. have been

C. has been

D. were

Answer: Option B

Solution(By Examveda Team)

In a sentence, if the subject is plural form then the verb form is must be a plural form.
In the given question, "The board of directors have been anxious."
This sentence has the following structure,
The board of directors- Subject (Plural form)
have been- Verb (Plural form).