on guard

• Ways for foreign trade enterprises to be on guard against exchange risk
  外贸企业如何防范汇率风险
• You should be on guard when a stranger is at your door
  6当陌生人站在你家门前时，你应该有所提防。
• There are soldiers on guard at the gate
  大门口有士兵在守卫。
• You should be on guard when a stranger comes to your doors
  当陌生人站在你家门前是,你应该有所堤防
• I was immediately on guard when father mentioned that incident
  父亲提起那件事，我就立刻提防起来。
• Stay on guard against dengue fever
  市民应采取措施预防登革热
• Stay on guard against mosquitoes
  市民应继续保持警觉防范蚊患
• Provides information on guarding against malicious user input
  提供有关防止恶意用户进行输入的信息。
• There are soldiers on guard at the gate
  大门口有士兵在守卫
• They should be certainly on guard
  他们早该防范一些的。