In the slow start phase of the TCP congestion algorithm, the size of the congestion window:
does not increase
In Slow start phase, window size increases by 1 MSS for each received acknowledgement and at the end of RTT, window size increases exponentially.
So, (D) is correct option!
Increase is exponential in the Slow Start Phase.
Answer is option D.
The tests are there but it ain't free. Cost is...