
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
Among the following statements, the correct propositions are  
① The radius of a sphere is the line segment from any point on the sphere to the center of the sphere;  
② The diameter of a sphere is the line segment between any two points on the sphere;  
③ Cutting a sphere with a plane results in a circle;  
④ The circle obtained by cutting a sphere with a plane not passing through the center of the sphere is called a small circle.

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