41. Oil and natural gas exist on this planet in a limited supply.
Therefore, it is essential for us to develop _____ to these
nonrenewable energy sources.
(A) alternatives
(B) explosives
(C) infinitives
(D) relatives
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統計: A(80), B(12), C(13), D(11), E(0) #3246276
統計: A(80), B(12), C(13), D(11), E(0) #3246276