Answer: Option (c) is the correct answer.
Step-by-step explanation:
Nervousness is a feeling of getting worried about something or showing anxiety over something.
For example, a student giving speech in front of whole school felt nervous and forgot lines from his speech.
Therefore, nervousness can make a person forget content that he has prepared to deliver.
Some signs of being nervous are sweating, biting nails, shaking of hands etc.
Thus, we can conclude that out of the given options, biting your nails is a gesture that suggests nervousness.