问题补充：
We would like to drop in at your house if
A. you are convenient
B. it is convenient of you
C. it is convenient to you
D. you will be convenient
答案：
A. you are convenient
B. it is convenient of you
(答案→)C. it is convenient to you
D. you will be convenient
解析：考查条件状语从句，if条件句不能用将来时，用一般现在时代替一般将来时，convenient这个词的主语不是sb，而是it，it’s convenient to sb某人方便的时候，句意是：如果方便的话我们想拜访你家。选C。
