粉尘中游离SiO2含量<10%，总粉尘最高允许浓度（）mg/m3。
A、3.5
B、2
C、10
参考答案：C
茯苓的功效是（）
A.利水通淋，清热排脓
B.利水消肿，渗湿，健脾，宁心
C.利尿通淋，清解暑热，收湿敛疮
D.利水渗湿，泻热，通乳
E.利水通淋，化痰止咳
He was in the mountain for a year. He felt as if he was ______
from the outside world.
A．cut out
B．cut off
C．cut up
D．cut through
