Verb conjugation of "sacrifier" in French

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I hope that I will have time to go skiing. Maybe it is even better to go at the end of the season. The doctor, however, did not give his diagnosis yet. If I cannot go I will have to find an alternative.
Why did you sit on the box? You obviously did not know that there were presents inside. Now, seriously, do you have a backup plan? We must buy new gifts if we want to go to the party.?