The Correct Option is B
Solution and Explanation
Approach: Rather than read all four heights, race only the front-runners. From the chart, Koushik and Suranjan are the two who get off to the fastest starts, so the winner at minute 20 is whichever of those two is ahead; the slower two cannot overtake.
Step 1: Eliminate the laggards. Anirbid and Chandranath are both still around the $5$-puzzle mark at $t=20$, so neither can be the leader.
Step 2: Compare the two fast starters at $t=20$. Suranjan stands at $6$ puzzles; Koushik stands at $7$. Koushik is the higher of the two.
Step 3: Conclude. The most puzzles solved by minute $20$ is $7$, by Koushik.
Final answer: Koushik.