Re: Which sentence is the correct one?
There shouldnt be any confusion in not trusting X2.
See it all depends on the context in which you are using it. Otherwise none is wrong.
Btw, here is how you should think. Take the same example in multiple sentences.
For example,
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A sentence you can think of.. Or, the sentence you can think of..
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Rems, a nick you have chosen.. Or Rems, the nick you have chosen..
HTH