The reason most Chinese have healthy white teeth is they eat a healthy diet.
A. why; that
B. why; because
C. that; that
D. for; that
网友回答
(答案→)A. why; that
B. why; because
C. that; that
D. for; that
解析：考查定语从句及名词性从句。句中why引导定语从句，先行词the reason在从句中作原因状语；that引导表语从句，故选A。