如果你饮食不当，可能会感到虚弱。

If you haven't eaten properly, you might feel ___weak.

流感过后，我感到如此虚弱，以至于无法做任何家务。

After the flu, I felt so ___weak that I couldn't do any chores.

长跑后，他的腿很虚弱。

His legs were ___weak after the long run.