multiply the channels of circulation

例句：

1. 1. The population of thecity has been increasing steadily for the pastdecade.
   过去十年里，这个城市的人口一直在稳步增长。
2. 2. The company's profitshave been multiplying thanks toits new product line.
   由于推出了新产品线，这家公司的利润正在不断增加。
3. 3. Thenumber of students in theclass is multiplyingevery year.
   班上的学生人数每年都在增加。