The teacher decided to reward the whole class with chocolates for their excellent performance in the exam.

reward 是动词，意思是"奖励、给予回报"。这个词由前缀 re-（表示"再次"）和 ward（古英语词根，意为"看护、关注"）组成，原意是"重新关注/回报某人的行为"，引申为"奖励"的意思。