it is of great use 为什么要用of 而不用a

it is of great use 为什么要用of 而不用a It is a waste of time doing this这里为什么用doing而不用do?为什么? Did you use to be afraid of the dark?为什么要用Did而不用Were. He is of medium hight 中为什么是用 is of 而不用 has a our question were about use of the Internet 为什么这个地方用use而不用us I found it of great interest.为什么用great不用very或者much A.It is of great fun. It[takes]them a lot of time.为什么用takes而不用pays,spends, it will save you a lot of time.为什么用you而不用?your It is wrong of you to ignore their avice.中为什么要用of,不用for? Is there a lot of furniture?后面有a lot of前面为什么要用be动词单数is而不用复数a there is a highway___the two cities.中为什么用between而不用of,in,amo