CORRECT answer is 'uncertain'.'Precarious' means dependent on chance, circumstances, unknown conditions, or uncertain developments.'Uncertain' means not knowing what to do or believe, or not able to DECIDE SOMETHING.Thus, precarious and uncertain are same in their MEANINGS and form a synonym pair.Let's understand the meanings of other given options:Painful - That causes pain or hurts.Hinder - To make something more difficult for somebody/something to do something.