–Who is the tallest boy?–It ______  be John. Because John is of medium height..

—Must I go to the shop with you，Mum?—Err... I can make it myself，Mike. You         go with me.

 Washington ______ get very hot and sticky in summertime. July and August are usually the warmest months.

If you _____ smoke, please go outside because this is a non-smoking office.

The doctor said he _______ an operation yet.