Revise and check 7 and 8

I need ________ some emails.

• to answer

• answer

• answering

The situation is difficult ________.

• for explain

• explain

• to explain

I don't know what ________.

• do

• to do

• that I do

I don't really mind _______ housework.

• do

• to do

• doing

______ is one of the best forms of exercise.

• Swiming

• Swimming

• Swim

______ bring our books tomorrow?

• Do we have to

• Have we to

• Do we must

It's free. You ______ pay.

• don't have to

• mustn't

• haven't to

You must ______ drink so much coffee.

• not should

• don't should

• shouldn't

You must ______your grandmother.

• to call

• calling

• call

I think you should _____ to her about it.

• to talk

• talk

• talking