Mia's plant grows at an average rate of 5cm each month.
When she bought it, it was 18 cm tall.

Select the function that models the relationship between y, the height of the plant in cm, and x, the time in months that it grows.

A. y = 18x + 5

B. y = 18 + 5x

C. y = x + 18

D. y = 23x