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)