In the following questions, a part of the sentence is underlined. Below are given alternatives to the underlined part at (a), (b) and (c) which may improve the sentence. Choose the correct alternative. In case no improvement is needed, your answer is (d).

Historians feel there is an earnest need for the review of history text books every five years and a revision of the same every ten years.

A. imperative

B. indispensable

C. urgent

D. No improvement

Please do not use chat terms. Example: avoid using "grt" instead of "great".