Each question below has two blanks, each blank indicating that something has been omitted. Choose the set of words for each blank that best fits the meaning of the sentence as a whole.

Drawing attention to the pitfalls of _________ solely on Uranium as a fuel for nuclear reactors, Indian scientists warned that Uranium will not last for long and thus research on Thorium as its must be revived _________.

A. using, substitute

B. believing, replacement

C. depending, reserve

D. relying, alternative

Please do not use chat terms. Example: avoid using "grt" instead of "great".