内曲球

例句：

1. 1. The inner curve of the ball is crucial for its stability.
   球的内部曲线对其稳定性至关重要。
2. 2. The inner curve of the ball affects its trajectory.
   球的内部曲线影响其轨迹。
3. 3. The inner curve of the ball is designed to enhance performance.
   球的内部曲线设计用于提高性能。