Biologists working in Spain say that their discovery of teeming life in a highly acidic river may not only broaden the search for life, or for evidence of past life, no other planets but also show that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all but the hardiest bacteria.

A. show that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all but the hardiest bacteria
B. may show that a number of forms of microscopic life is capable of adapting to conditions that
scientists have long thought hostile to all bacteria but the hardiest ones
C. shows a number of forms of microscopic life to be capable to adapt to conditions that scientists have long thought had been hostile to all but the hardiest bacteria
D. showing that a number of forms of microscopic life is capable of adapting to conditions that
scientists have long thought had been hostile to all but the hardiest bacteria
E. showing that a number of forms of microscopic life can adapt to conditions that scientists have long thought hostile to all bacteria but the hardiest

The OA given is A but i think in A there is a sub-verb agreement error..discovery (sing) should use sing shows in C...is there anything related to the use of MAY in the sentence...please explain????