在使用过滤式防毒面具时,空气中氧气含量应在()范围内,毒物浓度应小于()的环境方可使用。
参考答案:19.5—21.5%;1%
“西湖春色归,春水绿于染.”此处的“绿”主要指哪类植物( )
A.藻类植物
B.苔藓植物
C.蕨类植物
D.种子植物
When she first arrived in China, she wondered what the future might have ____ for her, but now
all her worries are gone. [ ]
A. in need
B. in time
C. in preparation
D. in store