Cook was a strict but good captain, _________ who, usually, took care of the sailors on his  ship.

—I don’t think we’ll be able to pass the driving test． —If we keep practicing , we, should make ___.

Haze (雾霾)appears around us. Let’s do ________ helpful to protect the environment.

—Mom, Bill is coming to dinner this evening.—OK. Let’s give him _________to eat.

—Who is the classroom now?—     . All the students are on the playground(操场)