We haven’t been told if they ( )on time.If they ( ),I will t

We haven't been told if they ( )on time.If they ( ),I will tell you immediately.
A.will arrive,will arrive B.arrive,arrive
C.will arrive,arrive D.arrive,will arrive

答案对,原因不太明了!这样也许更清晰——
1、选C.
句子意思：
我们未被告知他们【是否】会按时来.【如果】他们到了,我将立刻告知你.
考点：
if 的不同意思和引导不同从句的时态搭配.
关键：
if表示【是否】,引导宾语从句.时态依据句子意思和前后关系搭配使用.
这里,句子意思表示【是否将会来】,因此,用一般将来时.
if表示【如果】,引导条件状语从句.主句用一般将来时,if从句用一般现在时代替一般将来时.
所以,只有C正确.
2、
It is( )book that it is sold out within 30 minutes
A.such interesting a B.so a interesting
C.so interesting a D.a such interesting
选C.
考点：
such...that和so...that连接单数可数名词的结构.
知识链接：
such+a/an+形容词+单数可数名词
so+形容词+a/an+单数可数名词
例如：
She is such a good teacher that we all respect her.
=She is so good a teacher that we all respect her.
祝你开心如意!