frequency keying method

例句：

1. 1.The frequency of earthquakes in this area is relatively high.
   这个地区的地震频率相对较高。
2. 2.The frequency of occurrence of the disease is low.
   这种疾病的发生率很低。
3. 3. The frequency of traffic accidents has decreased significantly over the past decade.
   过去十年间，交通事故的发生频率显著下降。