Select the option which is the most appropriate one word substitution for the given group of words.

One who devotes one's life to the welfare of other people.

altruist

The most appropriate one-word substitution for the given group of words "one who devotes one's life to the welfare of other people" is altruist.

• Alchemist is a person who studies or practices alchemy, a medieval science that sought to transform base metals into gold.
• Martyr is a person who dies for a cause, especially a religious one.
• Altruist is a person who is concerned with the welfare of others and is willing to put their own interests aside for the sake of others.
• Ambassador is a person who represents one country in another country.

The word altruist is the most appropriate because it specifically refers to someone who is selfless and dedicated to helping others. The other words do not have the same connotation of being someone who is devoted to the welfare of others.