未知题型 This is not what we asked you to do. You can not get more pay for the _______ work. A.owing B.device C.tired D.extra

未知题型 When the airplane takes off， the passengers are told to _______ their seat belts. A.fountain B.fix C.tight D.fasten

未知题型 .Water and air are _______ to human beings. We can not live without them. A.harbour B.function C.definite D.essential