問題詳情

21. Hot-air ballooning _____ around for centuries, but many travelers still consider it asexciting as parasailing or bungee jumping.
(A) is
(B) was
(C) has been going
(D) has been

參考答案

答案:D
難度:適中0.415094
統計:A(7),B(1),C(20),D(22),E(0)