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Answer:
B, C
Step-by-step explanation:
The equation for the circumference C of a circle of diameter d is ...
C = πd
That is, π is the constant of proportionality between circumference and diameter.
Clearly, when the diameter is 1, the circumference will be π.
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π is the circumference when diameter is 1.
π is the constant of proportionality between circumference and diameter.
