Sentence Correction

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

OA: A

i got the right answer but one doubt....."show" must refer to "discovery" and therefore we must use in its singular form "shows" instead of plural. can anybody plz explain?