阿摩線上測驗
21. The origin of complex organisms called eukaryotes- which includes all animals, plants, and fungi- _____ one of biology’s biggest mysteries.
(A) is
(B) are
(C) being
(D) been
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統計： A(225), B(53), C(67), D(6), E(0) #3128948
統計： A(225), B(53), C(67), D(6), E(0) #3128948
