
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 propositions, the true ones are __________.  
① If two planes $\alpha \parallel \beta$, and $a \subset \alpha$, $b \subset \beta$, then $a \parallel b$;  
② If two planes $\alpha \parallel \beta$, and $a \subset \alpha$, $b \subset \beta$, then $a$ and $b$ are definitely skew;  
③ If two planes $\alpha \parallel \beta$, and $a \subset \alpha$, $b \subset \beta$, then $a$ and $b$ definitely do not intersect;  
④ If two planes $\alpha \parallel \beta$, and $a \subset \alpha$, $b \subset \beta$, then $a$ and $b$ are coplanar or skew;  
⑤ If two planes $\alpha \parallel \beta$, and $a \subset \alpha$, then $a$ and $\beta$ definitely intersect.

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