Explanation:

- Child: A child is not automatically considered incompetent as a witness. It depends on their ability to understand questions and give rational answers.

- Accused: The accused can be a competent witness in their own defense. They can testify voluntarily on their behalf.

- Lunatic: A lunatic, or person with mental illness, can be a witness if they can understand questions and provide rational answers when they are not in a fit of lunacy.

- All the Above: Section 118 of the Indian Evidence Act considers all individuals capable of understanding questions and giving rational answers as competent witnesses, barring other exclusions.

The correct answer is: All the above