Every few years, sailboats of different countries compete in a race for a trophy called the America's Cup. The boats sail over the same distance. What, besides the distance, is needed to find out the speed of each boat in the race?
a
the size of each boat in the race
b
the skill of the crew of each boat in the race
c
the time it takes each boat to finish the race
d
the speed of the wind during the race