The twins will go fishing with us this weekend _____ they are free.A though B if C whether D but
问题描述：
The twins will go fishing with us this weekend _____ they are free.A though B if C whether D but
答
B
条件状语从句,主将从现
如果双胞胎有空,他们就在这个周末跟我们去钓鱼