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

未知题型 .Please _______ me for my rudeness. I really do not know the custom here. A. engage B.comfort C.execute D.forgive