--- He looks so tired. What’s wrong? --- Nothing serious. He just stayed up last night, ___________his papers.

Mr. Benet is such a wise teacher. Never have I regretted           the advice he gave me.

 The April Fools' tradition is said ________ in the sixteenth century.

My mother has two brothers, both of ____ graduating from Beijing University．

Mr. Smith suggested the student ___ to be given a prize.