Question Type: Vocabulary

This question tests your vocabulary and understanding of prefixes and their meanings. Let's analyze each option:

• Pyromaniac: Someone with an uncontrollable obsession with setting fires.
• Psychomaniac: While not a standard psychological term, it suggests someone obsessed with the psyche or mind, often in a negative or deranged way.
• Egomaniac: Someone excessively conceited or self-centered.
• Monomaniac: Someone obsessed with a single idea or purpose. This fits the question's description perfectly.

The prefix "mono" means "one" or "single." Therefore, a "monomaniac" is someone fixated on one particular thing. The other options describe different types of obsessions or fixations, but not a singular focus.

Why other options are incorrect:

• Pyromaniac refers to fire obsession, not a single idea.
• Psychomaniac is not a standard term, and even if interpreted, it is not a precise fit.
• Egomaniac describes self-obsession, not a specific idea.

Therefore, the correct answer is Monomaniac.