Similar problems arose in connection with the street railways, electric light plants, and other utilities in the great cities.

——类似的问题也出现在大城市的街道铁路、电厂和其他公用设施方面。

While chlorophyll is the most common pigment that plants use to harvest light — green leaves look that way because chlorophyll absorbs red and blue light and reflects green light — plants often have a variety of secondary pigments, too.

绿叶之所以是绿的是因为叶绿素吸收红光和蓝光，反射绿光。虽然叶绿素是植物用来获取光能最常见的色素，但植物通常也有各种辅助色素。