Which one of the following most accurately expresses the main point of ... ...

Which one of the following most accurately expresses the main point of the passage?


(A) Although most organisms are known to produce several kinds of proteins, the mechanism by which isolated protein molecules such as prions reproduce themselves is not yet known in detail.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in PT70 (Oct 2013): Reading Comprehension