A.电磁波能在真空中传播
B.红外线不是电磁波
C.电磁波频率越高,波长越短
D.电磁波在真空中的传播速度是3×108m/s
答案:B
They make __________ dragon boats every year.[ ]
A. own their
B. own
C. them own
D. their own
颅后窝占位性病变出现枕骨大孔疝危象时,快速而有效的急救措施有()
A.速静脉推注呼吸兴奋剂
B.尽快行颅后窝开颅占位性病变切除术
C.及时行辅助呼吸
D.行脑室穿刺脑脊液体外引流术
E.静脉快速滴注甘露醇