He's sure to go if he___free.A.is B.will be原因?

He's sure to go if he___free.A.is B.will be原因?
He's sure to go if he___free.A.is B.will be原因?

He's sure to go if he___free.A.is B.will be原因?
A
IF 从句的一般将来时用一般现在时代替.
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A吧
if引导的条件壮语从句用现在时代替将来式

A
be sure to 一定；肯定
be free 空闲
翻译：他一定会去如果他有空。