Based on the ph tolerance level data in the chart, an appropriate research topic that would lead to valid conclusions would be represented by all but one of the research questions. that is: a) would a buffering solution increase the life span of frogs? b) what animal life forms seem most resistant to change in ph? c) how does a change in temperature affect the reproduction of crayfish? d) what is the effect of acid rain on animal life within a closed system?

I believe the answer is C)How does a change in temperature affect the reproduction of crayfish?  

The concentration of H+ ion (pH) could influence the structure of protein, which might inactivate some enzyme of an organism and alter their metabolism. All research questions beside option C is related to the pH. Buffer solution will provide an protection that will makes the pH become more stable. Acid rain contains acid which will decrease the pH of the surrounding environment.

b c a d mark me