Correct : a,d

The correct answers are A and D.
To understand why, let''s quickly walk through what actually happens during a TCP connection setup — commonly known as the three-way handshake.
When client P wants to connect to server Q, it sends a SYN (synchronize) segment. This SYN carries a sequence number N_P, which is called the Initial Sequence Number (ISN). Now here''s the important part — this number is not always 0. It is randomly chosen by the client. This is by design. TCP deliberately picks a random ISN to avoid security issues like session hijacking and to prevent old duplicate packets from a previous connection on the same port pair from being mistakenly accepted by a new session. So Option A is correct and Option B is wrong.
Once server Q receives the SYN with sequence number N_P, it replies with a SYN-ACK. In this SYN-ACK, the server sets the acknowledgement number to N_P + 1. This is TCP''s way of saying — "I received your SYN (which consumed one sequence number), and I''m now expecting the next byte starting from N_P + 1." So Option D is correct and Option C is wrong — NQ is not equal to N_P, it is N_P + 1.