医护人员随时待命，以便在紧急情况下提供支援。

Medical staff are on call to provide ___back ___up in case of an emergency.

确保你的电脑有可靠的备用电源，以防停电。

Make sure your computer has a reliable ___back ___up power supply in case of a blackout.

如果出现任何问题，我们的项目团队已准备好一个强有力的备用方案。

Our project team has a strong ___back ___up plan ready if any issues arise.