Final answer:
The TTR option of the CIRCLE command creates a circle of a specific radius that is tangent to two existing objects.
Step-by-step explanation:
The option of the CIRCLE command that creates a circle of a specific radius that is tangent to two existing objects is the TTR option. TTR stands for Tangent-Tangent-Radius. This option allows you to specify two points on the existing objects that the circle should be tangent to, as well as the radius of the circle.
For example, if you have two lines in a drawing and you want to create a circle that is tangent to both lines, you would use the TTR option and select the two points where the circle should be tangent to the lines.