(A) "Approaches to a problem..." "Efficient" - no problem needs solving and efficiency is discussed nowhere.
(C) "Flaws inherent" - one is not FLAWED, it just seems to be a bit more plausible.
(D) "Adopted two different mechanisms" - no. The biologists proposed that there may be two different hypothesis but the bacteria have only ONE mechanism. It is just up to the scientists to figure out which one that is.
(E) "One mechanism...more efficient..." - once again, this efficiency thing comes out of nowhere and the rest doesn't capture the nuance of the third paragraph.