In an Ethernet network, under what two scenarios can devices transmit?()
A. when they receive a special token
B. when there is a carrier
C. when they detect no other devices are sending
D. when the medium is idle
E. when the server grants acce
直角梯形的上底是4cm,下底是6cm,高是6cm,宽度是2cm,它的体积是()。
A. 20cm3
B. 30cm3
C. 50cm3
D. 60cm3
一静脉输液过程中的患者突然发生了呼吸困难、胸闷气促、咳嗽、咳泡沬痰和咳泡沬样的粉色痰,患者发生了()
A. 过敏性休克
B. 急性右心衰
C. 空气栓塞
D. 急性肺水肿