Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are FALSE with respect to the TCP connection? I. If the sequence number of a segment is $m$, then the sequence number of the subsequent segment is always $m+1$. II. If the estimated round trip time at any given point of time is $t$ sec, the value of the retransmission timeout is always set to greater than or equal to $t$ sec. III. The size of the advertised window never changes during the course of the TCP connection. IV. The number of unacknowledged bytes at the sender is always less than or equal to the advertised window.

Let us evaluate each statement:

• Statement I is FALSE: TCP uses byte-stream sequence numbering rather than segment numbering. If a segment starts with sequence number $m$ and contains $L$ bytes of payload data, the sequence number of the next segment will be $m + L$, which is generally not $m + 1$ (except when the segment carries only $1$ byte).

• Statement II is TRUE: The Retransmission Timeout (RTO) is calculated as $\text{RTO} = \text{SRTT} + 4 \times \text{RTTVAR}$ (or similar formulas based on Jacobson's algorithm), which ensures $\text{RTO} \ge \text{RTT}$ so that packets are not prematurely retransmitted before an acknowledgement can reasonably arrive.

• Statement III is FALSE: TCP uses a dynamic sliding window for flow control. The receiver continuously advertises its available buffer space (the Advertised Window or Receiver Window, rwnd), which dynamically changes depending on how fast the receiving application reads data from the buffer.

• Statement IV is TRUE: Flow control guarantees that the sender cannot have more unacknowledged in-flight bytes than the receiver's currently advertised window size.

Therefore, statements I and III are FALSE, making (B) the correct choice.