问题补充：
–Mary, could you tell me if your mother our school sports meeting tomorrow?
--I think she will come to school if she free.
A. will take part in, will be
B. takes part in, is`
C. will take part in, is
D. takes part in, will be
答案：
A. will take part in, will be
B. takes part in, is`
(答案→)C. will take part in, is
D. takes part in, will be
解析：第一句中，if 引导的是宾语从句，因此从句根据自己的时态需要决定，根据意思第一空用将来时，而后一句中if 引导的是条件状语从句，在if 引导的条件状语从句中如果主句为一般将来时，从句用一般现在时代替将来时，故选C
