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创建,开发 build ____
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举一反三
【单选题】可通过垂直传播的病毒有:
A.
风疹病毒、 CMV 、 HSV
B.
风疹病毒、流感病毒、 CMV
C.
风疹病毒、 VZV 、腮腺炎病毒
D.
风疹病毒、 HBV 、腺病毒
【单选题】What statement best describes a proximity sensor?
A.
An electronic switch that activates when in close proximity to a target
B.
A relay that activates when in close proximity to a target
C.
A solenoid that activates when in close proximity to a target
D.
A mechanical limit switch used to sense proximity of a target
【单选题】What statement best describes modulation?
A.
Imposing intelligence onto a radio carrier signal.
B.
Changing mark-space to 1 and 0.
C.
Adjusting the frequency to the optimum band for long distance communications.
D.
Converting the carrier from a low frequency to a higher frequency.
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