Context: You Ca n't Fool The Heart Rate MonitorA corollary to the expression , " You can fool some of the people all of he time , etc . " is that " you can never fool the heart rate monitor".This past Friday and Sunday , I did difficult 40 mile rides with my chavrusah . Trying to keep up with him was quite challenging but the results were excellent . I finished the ride in a personal best time and my average heart rate for the ride was around 80 % of my maximum heart rate .
Question Why is the narrator 's heart rate so elevated ?
Possible answers:

[a]. They just did a bike ride .;
[b]. They just did a marathon .;
[c]. They just did a stressful work event .;
[d]. None of the above choices .;
The answer:
[a].