Choose the greeting words which match with the given sentence
I’m tired, I am going to sleep.

The correct answer is: Good night

Greeting is a salutation at meeting and an expression of good wishes. Say good night only when you or other person is going to bed or leaving for the night. In English, good night is never actually a greeting but rather a farewell. 'I'm tired, I'm going to sleep', here 'good night' is appropriate because there is mentioned 'going to sleep'.