when did you become interested in snakes or when have you become?
I cannot understand the difference between them, can you make me understand, please?

Question

Answer

The second sentence is incorrect. You can not “have” something before it has become.

They now have an interest in snakes because they became interested in them in the past.

Answer

There isn't much of a difference- but I would always use the first option, 'when did you become interested'. I don't think I've ever heard someone ask when someone else 'has become interested' in something.

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