Which situation can be represented by a true proportion?

A: a store charged $20 for 2 shirts and charged $25 for 3 shirts

B: an alarm clock beeped 7 times in 6 seconds and beeped 14 times in 12 seconds

C: a car used 3 gallons of gas to drive 72 miles on a highway and used 4 gallons of gas to drive 72 miles in town

D: a signal light flashed yellow 7 times in 28 seconds and flashed red 5 times in 35 seconds.

plz help me