The sides of a triangle are in the ratio 3:4:5. What is the length of each side if the perimeter of the triangle is 30 cm?

A. 2.5 cm, 5. cm, 7.5 cm

B. 9 cm, 10 cm, 11 cm

C. 7.5 cm, 10 cm, 12.5 cm

D. 2.5 cm, 7.5 cm, 12.5 cm