Answer:
C. Samir stopped and stretched for 5 minutes.
Explanation:
We are given that,
Samir walked for 10 minutes, then stopped and stretched for 5 minutes, walked again for 20 minutes and ran for another 15 minutes
As, we can see that for the parts where Samir is walking or running, he is not in a constant or still state i.e. his position is changing.
But, during the stretching time, he is still at that position and his position is not changing.
Thus, the linear constant part of Samir's journey is represented by the time he stopped and stretched for 5 minutes.