The word astute means having or showing an ability to accurately assess situations or people and turn this to one's advantage. It implies being sharp and clever.
To find the antonym, we look for a word that conveys the opposite meaning.
Let's examine the options:
- sharp: This word is a synonym, meaning astute or keen. It is not an antonym.
- brilliant: While this can mean intelligent or clever, it does not oppose astute.
- ingenuous: This word means innocent or unsuspecting, suggesting a lack of cunning or sharpness. It is the correct antonym.
- prudent: This means acting with or showing care and thought for the future, not directly opposing astute.
Therefore, the correct antonym of astute is: ingenuous.