主要要素

例句：

1. 1. The main reason for his absence was due to a sudden illness.
   他缺席的主要原因是由于突发疾病。
2. 2. Maintaining good health is crucial for a happy life.
   保持健康对幸福生活至关重要。
3. 3. The main goal of the project is to improve efficiency.
   该项目的主要目标是提高效率。