B- The red horse's average speed was greater than the black horse's average speed.
Red average speed = 1/120 = 0.00833 mi/s
Black average speed = 1/150 = 0.00667 mi/s
we only know about average speed based on the information given. Either horse could have had higher or lower, even negative, instantaneous speed during some phase of the race.
there is no such thing as a red horse. there are chestnuts, bays and red roans, just no reds. usually though, blacks are faster scientifically than red roans.