(Choice A)
A
16+6+6+616+6+6+616, plus, 6, plus, 6, plus, 6

(Choice B)
B
16+6+6+6+616+6+6+6+616, plus, 6, plus, 6, plus, 6, plus, 6

(Choice C)
C
16+12+12+12+1216+12+12+12+1216, plus, 12, plus, 12, plus, 12, plus, 12

(Choice D)
D
16+1216+1216, plus, 12

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.