Which is correct? Or are they both OK? If they are both OK, do they have the same meaning?
If you think he is a nice guy, you are wrong.
If you think he is a nice guy, that's wrong.
And what about these two?
You may think he is a nice guy, but you are wrong.
You may think he is a nice guy, but that's wrong.
They are all OK, but #1 and #3 are smoother, ie they sound better.
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