Correct Answer: pacifist

Solution : The first option is the correct answer.

The term pacifist accurately represents a person who believes that war and violence are unjustifiable and actively advocates for peaceful solutions.

A pacifist is committed to non-violence and the promotion of peace as a fundamental principle.

The meanings of the other options are as follows:

• Anarchist refers to a person who opposes authority and advocates for the absence of a governing body or state.
• An optimist refers to a person who generally has a positive outlook and expects favourable outcomes.
• Pessimist refers to a person who generally has a negative outlook and expects unfavourable outcomes.

Therefore, the correct answer is pacifist.