Question

1. When you are not at home, who takes care of the children?

2. When you are not at home, who is taking care of the children?

3. When you are not at home, who will take care of the children?
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Which ones are correct and common?
Does #2 mean #3?
Can we use 'while' instead of 'when' to have the same meaning?

Answer 1

1 and 3 are closest in meaning, but really, all three mean about the same thing. And yes, in these sentences, "when" and "while" would mean the same thing.