Suppose the round-trip propagation delay for a 10 Mbps Ethernet having 48-bit…

For CSMA/CD collision detection, the sender must transmit long enough for a collision indication to propagate back. The round-trip propagation delay is 46.4 microseconds. At 10 Mbps, the number of bits transmitted during this time is 10 x 10^6 x 46.4 x 10^-6 = 464 bits. Since the Ethernet uses a 48-bit jamming signal, the minimum frame size required is 464 + 48 = 512 bits. Hence option D is correct.