Select the most appropriate ANTONYM of the underlined word in the given sentence.

We had hundreds of courageous scientists.

diffident

The most appropriate antonym of the underlined word courageous in the given sentence is diffident.

• Courageous means "having or showing courage."
• Diffident means "lacking self-confidence; shy."

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

• Gutsy means "having or showing courage or determination."
• Audacious means "daring or bold in a way that shows a lack of respect for danger or convention."
• Valiant means "showing or having courage in the face of danger or difficulty."