$\textbf{Answer: (D) The client and server can initiate closing of the connection at the same time}$
$\textbf{Explanation:}$
$\textbf{(A) Incorrect}$
TCP uses a $\textbf{3-way handshake}$ for connection establishment, not a two-way handshake.
\[\text{Client} \rightarrow \text{Server} : SYN\]
\[\text{Server} \rightarrow \text{Client} : SYN + ACK\]
\[\text{Client} \rightarrow \text{Server} : ACK\]
$\textbf{(B) Incorrect}$
In TCP, either client or server can initiate connection termination using $\textbf{FIN segments}$. There is no restriction that only the client can initiate closing. Both client and server can initiate termination, even simultaneously.
$\textbf{(C) Incorrect}$
TCP is a $\textbf{full duplex, connection-oriented protocol}$, not half duplex. Both sender and receiver can transmit data simultaneously.
$\textbf{(D) Correct}$
Either client or server can initiate connection termination using $\textbf{FIN segments}$. Both sides can even initiate termination simultaneously.
TCP connection termination follows a $\textbf{4-way handshake}$:
\[
\begin{array}{c|c}
\textbf{Client Initiation} & \textbf{Server Initiation} \\
\hline
\text{Client} \rightarrow \text{Server} : FIN & \text{Server} \rightarrow \text{Client} : FIN \\
\text{Server} \rightarrow \text{Client} : ACK & \text{Client} \rightarrow \text{Server} : ACK \\
\text{Server} \rightarrow \text{Client} : FIN & \text{Client} \rightarrow \text{Server} : FIN \\
\text{Client} \rightarrow \text{Server} : ACK & \text{Server} \rightarrow \text{Client} : ACK \\
\end{array}
\]
