The dimensions of an office conference room are 10 feet by 18 feet. If the conference room blueprint dimensions are 5 centimeters by 9 centimeters, what is the scale of the blueprint?
A. 1 centimeter = 9 feet
B. 1 centimeter = 2 feet
C. 1 centimeter = 5 feet
D. 1 centimeter = 10 feet