Yesenia swims laps at a pool. For every 10 laps she swims the backstroke, she swims 15 laps of freestyle.
Which ratio shows the number of laps Yesenia swims the backstroke to the number of laps she swims freestyle?
A. 2 : 3
B. 2 : 5
C. 3 : 2
D. 5 : 2