I found him to be a diligengt student. 应填 to be. 本题主要看found后面的代词是主格还是宾格. 1、I found him to be a diligengt student (to be a clever boy是him的宾语补足语.句型:find sb/sth ( to be )+adj./n./adv.觉得某人或某物.) 2、I found he was a diligengt student.(found后接宾语从句,从句谓语动词was 与主句的时态一致)