An IPv4 packet consists of a header and a payload:
Total Length=Header Length+Payload Length\text{Total Length} = \text{Header Length} + \text{Payload Length}Total Length=Header Length+Payload Length
* Given:
* IPv4 header length = 20B
* Total packet length = 1500B
Payload=1500B#20B=1480B\text{Payload} = 1500B - 20B = 1480BPayload=1500B#20B=1480B
* Option A (Incorrect): 1520B is incorrect because it exceeds the total packet length.
* Option B (Incorrect): 20B is just the header, not the payload.
* Option C (Incorrect): 1500B includes the header, not just the payload.
* Option D (Correct): 1480B is the correct payload size.
Thus, the correct answer is D (1480B).