He felt gratified to the old man for his help.

Answer: Option D

Gratified : give (someone) pleasure or satisfaction.
Depressed : (of a person) in a state of unhappiness or despondency.
Discouraged : having lost confidence or enthusiasm; disheartened.
Distressed : suffering from extreme anxiety, sorrow, or pain.
Frustrated : feeling or expressing distress and annoyance resulting from an inability to change or achieve something.

Antonym of Gratified is Frustrated