空调系统带冷（热）源的正常联合试运转时间不应少于（）
A.2h
B.8h
C.16h
D.24h
参考答案：B
People have planted a great many trees in order to ________ wind and sand in the desert.[ ]
A. hold down
B. hold up
C. hold back
D. hold out
巴金激流三部曲
