The following questions present a sentence

问题：

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence, you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

Every lawyer knows that it is difficult to prove culpability in technically complicated lawsuits if there is a lack of some expert to testify about the complicated technical aspects.（）

A. if there is a lack of some expert to testify

B. unless there will be an expert who might testify

C. should there be no testimony from an expert

D. without an expert’s testimony

E. lacking some expert to testify