
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
In the $xy$-plane, the segment with endpoints $(-3,0)$ and $(21,0)$ is the diameter of a circle. If the point $(x,12)$ is on the circle, then $x=$
**A)** 6
**B)** 9
**C)** 12
**D)** 15
**E)** 18

Present the answer in LaTex format: \boxed{Your answer}
user