A guy is riding his bicycle on road in the early morning at 8.7 m/s when he spots a large construction site 12.4 m in front of him. He applies the brakes and has an acceleration
of -2.7 m/s/s. Does the guy stop in time, or does he fall into the construction site?

No because a circle or pie graph usually shows percentages you'd need a line graph

Ithink it is a. but i'm not 100 percent sure.

Repeated trials allow you to calculate a mean which can reduce the effect of random errors to make your results more precise.your results will also be reproducible therefore if someone else did the same experiment they'd get the same results which would make your results more reliable.