Daily homework is necessary, _too much of it may bring harm to students.
A.so B.for C.but D.or
C
【解析】
句意:日常家庭作业是必须的,但是太多也许会伤害到学生。A. so 因此; B. for 为了; C. but 但是; D. or或者,否则;根据Daily homework is necessary日常家庭作业是必须的,和too much of it may bring harm to students.太多也许会伤害到学生之间是转折关系;故选C