19. They haven’t _____ an AIDS vaccine.
(A) yet developed
(B) developed already
(C) developing
(D) developing yet
(E) already developing

答案：登入後查看
統計： A(205), B(22), C(10), D(12), E(14) #820509

詳解 (共 2 筆)

麻糬OuO

B1 · 2019/03/04

#3227463

They haven’t _____ a...

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Linnea

B2 · 2026/05/14

#7371234

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