如果火车票售罄，我们可以考虑其他替代方案。

If the train tickets are sold out, we can consider other ___alternatives.

如果你没时间看医生，视频咨询是个不错的选择。

If you don't have time to see a doctor, video consultation is a good ___alternative.

如果牛奶喝完了，豆奶是个不错的替代品。

If we run out of milk, soy milk is a good ___alternative.