We should often keep _____ touch with each other, because we are good friends.
I don’t know if he_________here. If he ___________tomorrow, I will tell you.
The world’s population is getting larger and larger, so scientists are trying to ______ new ways to solve the food shortage.
He finds watching movies ______because the people speak too quickly.
E-mail is very popular today. People hardly post letters, _________?
—Who helped Jessie with her English?—_______, she taught herself.