Paul doesn t have to be made _______ . He is always a hard-working student. [A] stud

Going “green” （)have to be a challenge.A、 don’tB、 doesn’tC、 is

There happened to be some students in the room, ______？A．didn"t theyB．didn"t thereC．doesn"

He is not in the office. He must have gone to have classes, ______ ？A．didn"t heB．doesn"t h

I certainly didn t appreciate______when I made mistakes.A．to be accusedB．having accusedC．t

Experiments have to be made under carefully _____ conditions .A.treatedB.suppliedC.re

We have made up laws to protect the water from being polluted and the animals _____