Answer:
The correct answer option is: C = pi × 4.
Explanation:
We are given the diameter of a circle to be 4 cm and we are to determine which of the given equations can be used to find its circumference.
We know that the circumference of a circle is given by:

If diameter is 4 cm so the radius will be 2 cm so substituting it in the above formula to get the equation.
C = 2 × pi × 2 = pi × 4