The reason he could not go there was his grades were too low.
A. why ; because
B. that; because
C. why; that
D. that; that
网友回答
A. why ; because
B. that; because
(答案→)C. why; that
D. that; that
解析：考查名词性从句。The reason why … is / was that …，……的原因是……。Why引导定语从句，先行词reason在从句中作原因状语，that引导表语从句。故选C。