Because of verb tense? All of the other verbs (namely IS) is in the present tense, while claimed is in the past. Just my two cents.

Yes@milan you are correct. A is incorrect because of verb tense. Here is the official explanation:

"This question is primarily testing your ability to identify and correct an error in verb tense. Notice that the sentence's independent clause contains a main clause and a subordinate clause. In order for this sentence to make sense chronologically, both of the verbs in these clauses need to be in the same tense. "

I can see how the verb tense is different. But somehow when I read choice E, I feel that the simple present tense makes it sound as if the sentence is stating a habit rather than a one time event that took place. In fact since present continuous tense is used "is being", I don't see anything wrong with choice A. For example, can I not say something like this:

The lawyers made the claim that animals are being tortured in the dermatologists' experimental studies.

What is wrong with the above sentence?

Any opinions are welcome...

Yes.. all the verbs are in Present tense. that's what A is correct.