额外供应品将随时可用，如果需要的话。

Extra supplies will be ___on ___hand, should they be needed.

父母应该随时在手边帮助孩子做作业。

Parents should be ___on ___hand to help their children with schoolwork.

为了安全，厨房里总是放一个灭火器在手边。

Always have a fire extinguisher ___to ___hand in the kitchen for safety.