
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 tetrahedron P-ABC, PA, PB, and PC are mutually perpendicular, and PA=PB=PC=1. Among the following conclusions, the correct ones are ①PA⊥BC ②△ABC is an equilateral triangle ③The volume is $\frac{1}{2}$ ④The surface area is $\frac{3+ \sqrt{3}}{2}$. Fill in the correct serial numbers \_\_\_\_\_\_.

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