The youths are taught how to spray paint cars and mend fences.年轻人正在学习如何给汽车喷漆和修理围栏。Because of the immunity of the immature insects, it's important to spray regularly.由于幼虫对药物有免疫力，因此必须经常喷药。Farmers have to apply for permits to spray from the air.农民在申请得到许可后才能从空中喷洒农药。