Sentence Correction (SC) | Re: Researchers agreed that the study of new treatments for

the answer requires a That after but , so A and B eliminated.

D : The use of was in describing the ultra sound procedure is incorrect, because the ultra sound procedure must be in a simple present form , it requires "is" . so D is ruled out,
E: too wordy and improper construction. use is or is not any better muddles the while sentence.

So C

be generous with kudos

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