正解:C
Desired Min TX Interval: This is the minimum interval, in microseconds, that the local system would like to use when transmitting BFD Control packets, less any jitter applied. The value zero is reserved.
Required Min Echo RX Interval: This is the minimum interval, in microseconds, between received BFD Echo packets that this system is capable of supporting, less any jitter applied by the sender.
If this value is zero, the transmitting system does not support the receipt of BFD Echo packets.
Reference: https://tools.ietf.org/html/rfc5880