Question

the findings regarding the arsenic - using bacteria were ultimately considered uncertain and largely \debunked\ because:
a. the scientists found a seventh element essential for life.
b. the bacteria were found to be extraterrestrial in origin.
c. the arsenate ion proved to be chemically unstable in biological processes, and the original study could not be replicated.
d. scientists concluded that elemental substitution is impossible under any circumstances.

Explanation:

The arsenic - using bacteria findings were debunked because the arsenate ion was chemically unstable in biological processes and the original study couldn't be replicated. Option A is incorrect as it's the opposite of what happened (the claim was not supported). Option B has no basis in the debunking. Option D is too extreme as elemental substitution is possible in some cases but not here.

Answer:

C. The arsenate ion proved to be chemically unstable in biological processes, and the original study could not be replicated.