Pi is the ratio of to
a. area to diameter
b. perimeter to area
c. radius to diameter
d. circumference to diameter

Ineed to know the answer to this algebra question.

Amir wants to proportionally increase the size of a photo to create a poster for his room. the size of the original photo is shown. complete the statement and then answer the question to represent ways that amir can increase the size of his photo.

Which of the following circles have their centers on the x-axis? check all that apply.