高清电视直播对通讯信道有哪些要求?()
A.不超过40毫秒的端到端延迟
B.不低于10Mbps的上行带宽
C.有保证的网络质量
D.不超过20毫秒端到端延迟
参考答案:A, B, C
We the postcards yesterday, but it didn’t arrive.
A.should receive
B.ought to receive
C.ought to have received
D.must have received
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