阿摩線上測驗
16. For best viewing, NASA advises ______ to lie flat on their back in a region away from light pollution.
(A) participants
(B) passengers
(C) organizers
(D) spectators
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統計： A(10), B(4), C(1), D(23), E(0) #3449299
統計： A(10), B(4), C(1), D(23), E(0) #3449299
