The correct option is A Saving
The word 'squandering' refers to wasting something in a foolish and reckless manner.
Option A, discarding refers to getting rid of something as no longer useful or desirable.
Option B, saving refers to preventing waste of particular resource.
Option C, donating refers to giving something for a good cause.
Option D, stealing refers to taking someone's property without permission or legal right and without intending to return it.
Thus, according to the meaning, the word 'saving' is the opposite of the word 'squandering'.