periodic sample

例句：

1. 1.The temperature changes in a cyclical pattern every year.
   温度每年以周期性模式变化。
2. 2.The cycle of life is cyclical, repeating itself every few years.
   生命的循环是周期性的，每隔几年就会重复一次。
3. 3. The moon has a regular cycle of phases that repeats every 29.5 days.
   月亮有固定的周期，每29.5天重复一次相位变化。