What is the formula for the circumference of a circle?

The formula for the circumference of a circle is indeed expressed as C = (π)d, where C represents the circumference and d stands for the diameter of the circle. This relationship indicates that the circumference is proportional to the diameter, with π being the constant of proportionality.

In more practical terms, since the diameter is the distance across the circle through its center, multiplying the diameter by π yields the total distance around the circle. This formula is foundational in geometry, commonly used in various applications where calculating boundaries or circular distances is necessary.

The other options present different formulas related to circles but do not accurately define the circumference. For instance, C = 2(π)r also correctly defines the circumference, as it incorporates the radius, but it is not the direct form of the circumference in terms of diameter. C = πr^2 relates to the area of a circle, not its circumference, and C = (π)d^2 incorrectly suggests a squared term, which does not align with the properties of a circle's perimeter.