As a frame leaves a Layer 3 device,the Layer 2 encapsulation information is changed from what it was when it entered the device. For what two reasons can this happen?()
A. The data is moving from 10BASE-TX to 100BASE-T
B. The WAN encapsulation type has changed.
C. The data format has changed from analog to digital.
D. The source and destination hosts are in the same subnet.
E. The source and destination MAC addresses have changed.
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光电倍增管是()扫描仪常采用的光电转换器件。
A. 平台式
B. 滚筒式
C. 手持式
D. 反射式
M18螺母所对应的套筒型号是()。
A. S21
B. S24
C. S27
D. S30
对可疑气层进行井壁取心时,应及时(),并做含气、含油试验。