main nutrient elements

例句：

1. 1.The main reason for the delay is dueto the heavy traffic.
   延误的主要原因是由于交通拥堵。
2. 2. Maintaining good health is essentialfor a happy life.
   保持健康对于幸福的生活至关重要。
3. 3. The main goal of the projectis to improve efficiency.
   该项目的主要目标是提高效率。