阿摩線上測驗
21. The world would have changed for the better _____ the important lessons from the two world wars.
(A) if people learn
(B) had people learned
(C) if people have learned
(D) people had learned
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統計： A(19), B(32), C(57), D(6), E(0) #3007627
統計： A(19), B(32), C(57), D(6), E(0) #3007627
