Answer
The circumference will be doubled when the radius is doubled.
Work Step by Step
Let $C$ be the circumference of a circle:
$C=2 \pi r$ or, $C=\pi d$
Let us consider doubling the radius:
$C_{new}=2\pi (2r)=2(2\pi r)=2C$
Therefore, we can find that the circumference will be doubled when the radius is doubled.
