In the sentence, certain words are in bold and numbered from A to E, which are the possible pairs to be interchanged.Choose the pair(s) of words which need to be interchanged to make the sentence grammatically correct and meaningful.

While the research has (A)done the bug and some of its key (B)characteristics, much work remains to be (C)identified before it can be used to (D)treat large amounts of (E)waste plastic.