問題詳情

33．Most birds find it safe to sleep in the trees, but ________ they have eggs or young chicks, they don’t use a nest.
(A)why
(B)how
(C)unless
(D)where

參考答案

答案：C
難度：適中0.5
統計：A(0),B(0),C(0),D(0),E(0)