Select the option that can be used as a one-word substitute for the given group of words.

Easily provoked

Irascible

"Irascible" is an adjective that describes someone who has a tendency to become easily angered or provoked. It implies a quick or readily provoked temper or irritability. In the given group of words, "easily provoked," the word "irascible" accurately conveys the meaning of being easily angered or provoked.

"Invincible" means incapable of being defeated, overcome, or destroyed. It does not relate to being easily provoked or angered.

"Iridescent" refers to displaying a play of lustrous colors that change as the angle of view or the angle of light changes. It does not relate to temperament or being easily provoked.

"Irrational" means not based on reason or logic, or lacking sound judgment. While it can relate to emotions, it does not specifically indicate being easily provoked.

Therefore, "Irascible" is the most appropriate one-word substitute for the given group of words as it directly represents someone who is easily provoked or prone to anger.