Sentence Correction

Although the Supreme Court ruled as long ago as 1880 that Blacks could not be excluded outright from jury service, nearly a century of case-by-case adjudication has been necessary to develop and enforce the principle that all juries must be drawn from "a fair cross section of the community."
(A) has been necessary to develop and enforce the principle that all juries must be
(B) was necessary for developing and enforcing the principle of all juries being
(C) was to be necessary in developing and enforcing the principle of all juries to be
(D) is necessary to develop and enforce the principle that all juries must be
(E) will be necessary for developing and enforcing the principle of all juries being

OA A Why not D

This is a very simple question. Here is my explanation:

According to the question, the law was passed somewhere in 1880s but the adjudication is continuing even after a century.
Only option 'A' uses the form 'has'. So it is the correct answer.

(A) has been necessary to develop and enforce the principle that all juries must be (correct)
(B) was necessary for developing and enforcing the principle of all juries being(The adjudication is not over yet)
(C) was to be necessary in developing and enforcing the principle of all juries to be(The adjudication is not over yet)
(D) is necessary to develop and enforce the principle that all juries must be ('is' means that the adjudication is not taking place from 1980s and it is necessary to do it)
(E) will be necessary for developing and enforcing the principle of all juries being(We are not going to the future)