Her father was too tired too much hard work.
A. because
B. as
C. for
D. because of
网友回答
A. because
B. as
C. for
(答案→)D. because of
解析: because表示直接的,笼统的原因。后只可跟句子,它可用于句首或句子中间;as 表示比较明显的原因,后可跟名词短语或句子,但它不能用于句首;for表示推测的理由,只可跟名词短语,也只可用于句子中间;because of 后只可跟名词短语来表原因,可用于句首或句中间。句意:因为太多的艰苦工作,他的父亲太累了。比较直接地原因,后面为名词短语,故选D。