
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
Given that $a$ and $b$ are non-perpendicular skew lines, and $\alpha$ is a plane, the projections of $a$ and $b$ onto $\alpha$ could possibly be: ① two parallel lines; ② two perpendicular lines; ③ the same line; ④ one line and one point outside that line.

Among the above conclusions, the correct conclusion numbers are __________. (Write down all the correct conclusion numbers)

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