问题
选择题
This is a process happens when land becomes desert people cut down trees and dig up grass.
A．when; because
B．that; because of
C．when; because of
D．which; because
答案
答案：D
本题修饰名词process是一个定语从句，关系词用that或which，本题后半句跟的是一个原因状语从句，用because来连接，故本题只能选D。