I t is___to say "Thank you." when you get something from others.

题目

I t is___to say "Thank you." when you get something from others.
A a bad manner B bad maners C a good matter D good matters 选什么呢?

答案

It is a good manner to say "Thank you." when you get something from others.
'It' 形式主语,真正的主语是 to say " Thank you." 系动词是 is,单数形式,所以用 a good manner.
还原：To say " Thank you." is a good manner when you get something from others.