Jessica planted a rosebush in her garden. The rosebush has a height of 30 cm. Each month the rosebush increases by cm. Which equation can be used to determine the height of the plant in centimetres, y, after x months?
A) y = 30 - 6x
B) y = 6x - 30
C) y = 6x + 30
D) y = 6(x - 30)