Choose the correct one-word substitute for:
‘A person who avoids pleasures and lives with strict self-discipline’.

The correct option is Ascetic.

Explanation:

Let's understand the meaning of the given options to find the correct one-word substitute:

1. Ascetic: A person who practices severe self-discipline and avoids all forms of indulgence or pleasure, usually for religious or spiritual reasons.

2. Skeptic: A person inclined to question or doubt accepted opinions, facts, or claims.

3. Mystic: A person who seeks absorbing contemplation or surrender to God or divine reality through spiritual detachment.

4. Agnostic: A person who believes that nothing is known or can be known about the existence or nature of God.

Therefore, the word that best describes ‘A person who avoids pleasures and lives with strict self-discipline’ is Ascetic.