Which word in the given sentence is the ANTONYM of - doubtful?

The poverty of his childhood played a decisive role in his adult life.

decisive

The word decisive is the antonym of doubtful.

• Doubtful means "not certain or sure; undecided."
• Decisive means "having the power to decide or settle something; final."

Therefore, the word decisive is the opposite of doubtful. In the sentence, the poverty of his childhood played a decisive role in his adult life, meaning that it was a major factor that influenced his life. This is the opposite of being doubtful, which means not being certain or sure.

The other words in the sentence do not have the same meaning as doubtful, so they are not its antonyms.

• Played means "to act or perform a part."
• Adult means "a person who is fully grown or developed."
• Poverty means "the state of being poor."