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
网友回答
A. hold down
B. hold up
(答案→)C. hold back
D. hold out
解析：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。