Question

20. I just don't understand    that leads to so many teenagers becoming so addicted to the Internet.

A. why it does     B.  what does it

C. what it is      D.   what is it

Answer 1

20.   C考查强调句。句意：我就是不明白是什么导致如此多的青少年沉迷于互联网。句中understand之后的宾语从句部分为强调句的特殊疑问结构，强调句子的主语，故要用"what is it that..."，但受宾语从句的语序影响，要将该强调句变成陈述语序，由此可知，答案为C。