The correct answer is (A) To snack; to peck; to take small, quick bites of; to bite gently or cautiously; to eat or feed by biting off small bits.

Nibble comes from Low German nibbelen (to gnaw or pick at gently).

Examples of use:

• After the exercise, he was so exhausted that he could only nibble at his food.
• They nibbled on her freshly baked cookies while they discussed it.