Answer
The highest score by a right-handed batsman in the history of Test cricket is 374, which was made by Mahela Jayawardene of Sri Lanka against South Africa in 2006. Jayawardene batted for 570 minutes, facing 548 balls and hitting 43 fours and 6 sixes. His innings helped Sri Lanka to a total of 756/5 declared, which is the highest total ever scored in a Test match.