1-C. He's an enthusiastic, if not a gifted, player.He's an enthusiastic, if not a gifted, player.
彼は熱狂的な、天分豊かではないかもしれないが、プレイヤーです。
2-C. All the teachers were friendly and enthusiastic, and they sometimes stayed late to help us with our projects.All the teachers were friendly and enthusiastic, and they sometimes stayed late to help us with our projects.