问题
选择题
People have planted a lot of trees and grass in order to ____ wind and sand in the desert．
A．hold down
B．hold up
C．hold back
D．hold out
答案
答案：C
hold down 压制，限制；hold up推迟，耽搁；hold back 阻挡，抑制； hold out提供，提出。句意：人们种了大量的树和草，为了阻挡风沙。