primary rule

例句：

1. 1. The primary rule ofthe game is to keep the ball inplay.
   游戏的首要规则是保持球在比赛中。
2. 2. The company's policy on diversityis a fundamental rule for its success.
   公司关于多样性的政策是其成功的基础规则。
3. 3.The teacher emphasized the importance of followingthe primary rule of safety.
   老师强调了遵守安全的首要规则的重要性。