21) C
Franco’s study does not specify exactly when people started exercising.
A – Wrong
Not a conclusion as there is no mention of when people started exercising.
B – Wrong
The statement cannot be a reason for the conclusion.
C – Correct
The evidence given in the passage does not support about when people start exercising.
D – Wrong
The statement given in the question does not explain anything
E – Wrong
The statement given in the question does not counter Franco’s study
