Answer: D. The ratio of a circle's circumference to its diameter
Step-by-step explanation:
Pi is the ratio of the circumference of a circle to its diameter which means that we get pie by dividing the circumference by the diameter. This relationship is true regardless of the size of the circle because the relationship between the circumference and the diameter does not change regardless of size.
Pi is very useful when calculating measures related to circles such as area and circumference. It also comes in handy for shapes that have circles in them such as cones.
