
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
Using the oblique projection method, we get:  
① The intuitive diagram of a triangle must be a triangle;  
② The intuitive diagram of a square must be a rhombus;  
③ The intuitive diagram of an isosceles trapezoid can be a parallelogram;  
④ The intuitive diagram of a rhombus must be a rhombus.  
Among the above conclusions, the correct one is.

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