Answer:
The ratio that compares the diameter of the first circle to the diameter of the second circle is

Explanation:
Circumference of a circle:
The circumference of a circle of diameter d is given by:

In which d is the diameter.
One circle has a circumference half as large as that of a second circle.
We have that:

So

Simplifying by



The ratio that compares the diameter of the first circle to the diameter of the second circle is
