Daniel is one of the students in the class who never _______ a mistake even when it is pointed out to him.
Many people in the west make ________ a rule to buy Christmas presents for their relatives and friends.
They were all very tired, but ________ of them would stop to take a rest.
Come and see me whenever ________.
--The plane is due to take off at 7∶50 from the airport. --________ we fail to arrive there in time?
--They ________ out the problem, but failed. --What a shame ! I never thought it was going to happen like that.