he can hardly read is he is slow in mind.
A. what; that
B. That; what
C. What; because
D. That; because
网友回答
A. what; that
B. That; what
C. What; because
(答案→)D. That; because
解析：考查名词性从句。句中that引导主语从句，从句中不缺少任何成分；because引导表语从句，在从句中作原因状语。句意：他不能阅读是因为他思维慢。故D正确。