question_answer

If the radius of a circle is 'a' units, which of the following is its circumference?

A)  \[\text{2 }\!\!\pi\!\!\text{ a units}\]                     

B)  \[\text{ }\!\!\pi\!\!\text{ d units}\]       

C)         \[\text{2 }\!\!\pi\!\!\text{ d units}\]     

D)        \[\frac{\text{2 }\!\!\pi\!\!\text{ }}{a}\text{ units}\]