The correct answer in this question is option 4: To choose to ignore behavior that you know is wrong.

The idiom "turn a blind eye" is often used to describe a situation where someone purposely chooses to ignore or overlook something, particularly when that something involves inappropriate or wrong behavior. It implies that the person is aware of the wrongdoing but deliberately decides not to acknowledge or take action against it.

Option 1 - To run away, is not an accurate meaning for the idiom. It does not imply any form of physical escape or fleeing.

Option 2 - To begin to behave in a more positive manner, is completely unrelated to the idiom "turn a blind eye". It does not capture the concept of ignoring wrong behavior.

Option 3 - To change a situation, is also unrelated to the idiom. "Turn a blind eye" does not suggest making changes or altering a particular situation.

Therefore, option 4 - To choose to ignore behavior that you know is wrong, is the most appropriate expression to define the meaning of the idiom "turn a blind eye".