问题补充：
Today，we’ll discuss a number of cases beginners of learning English fail to use the language properly.
A. which
B. as
C. why
D. where
答案：
A. which
B. as
C. why
D. where
解析：D
解析此句中cases表示“情况”，这里where相当于in which，在从句中作状语。当先行词为case，stage，point等，且从句中不缺主要成分时，常用where引导定语从句，在句中作状语。
