在真空环境中不能传播的是( )
A.次声波
B.红外线
C.紫外线
D.激光
红外光、紫外线和激光,属于电磁波,都能在真空中传播;次声波是属于声波,不能在真空中传播.
故选A.
— I think students should have mobile phones to call their parents at school..
—_______. They often use them to play games instead.
A.I hope so
B.I don't agree
C.No problem
D.Good idea
下列哪种情况不是重度胎盘早剥的临床表现()
A.剧烈腹痛后 * * 流血
B. * * 出血量与全身症状不成正比
C.子宫底升高
D.子宫板状
E.胎位、胎心清晰