A.C.three-phase four-wire system with neutral earthed

例句：

1. 1. The A.C.system is widely used in modern homes.
   A.C.系统在现代家庭中被广泛使用。
2. 2. The A.C. system has many advantages over traditional heating and cooling systems.
   A.C.系统比传统加热和冷却系统有许多优点。
3. 3. The A.C.system can provide comfortable living conditions for people in hot weather.
   A.C.系统可以为炎热天气中的人们提供舒适的生活环境。