Select the most appropriate word for the given group of words.

Extreme physical or mental sufferings

Agony 

The option words have the following meanings:

- Agony : intense and prolonged physical or emotional pain, suffering, or distress.

- Autonomy : the state or condition of having the freedom and independence to govern oneself or make decisions without external influence or control.

- Aviary : An "aviary" is a large enclosure or cage designed to house and keep birds, particularly various species of birds kept for exhibition, breeding, conservation, or as pets.

- Autocracy :  a form of government where a single person, known as an autocrat or absolute ruler, holds all the political power and authority.

- Thus, "agony" is the most suitable substitute for 'extreme physical or mental sufferings'.