阿摩線上測驗
36. Supporters of hydrogen power explain _____ as an energy source, as water and heat are the only byproducts.
(A) how clean it is
(B) how clean is it
(C) how it clean is
(D) how is it clean
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統計： A(278), B(43), C(21), D(15), E(0) #2106462
統計： A(278), B(43), C(21), D(15), E(0) #2106462
