なら
A statement of the form “noun A なら predicate X” says that the predicate X applies only to A and is not more generally valid. The main ideas of a なら sentence, in other words, are “limitation” and “contrast”.
Ex: Q:ブラジルに行ったことがありますか。
Have you ever been to Brazil?
A:メキシコなら行ったことがありますが、ブラジルは行ったことがありません。
I’ve been to Mexico, but never been to Brazil