What is the maximum allowable round-trip time if a speed of 1 Gb/s needs to be achieved?

Refer to the exhibit.

A single file transfer is executed between Server A in Site A and Server B in Site B.
What is the maximum allowable round-trip time if a speed of 1 Gb/s needs to be achieved?

A.
500 microsec

B.
10 ms

C.
1 ms

D.
50 ms