阿摩線上測驗
15. Before they _______, they had both been diving instructors.
(A) had retired
(B) have retired
(C) are retiring
(D) retired
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統計： A(47), B(53), C(10), D(427), E(0) #217924
統計： A(47), B(53), C(10), D(427), E(0) #217924