because在这里有哪些用途

Not only is smoking bad for your health,its the source of social problems in developing countries because, since profit from tobacco is very high, tobacco has taken up the best food-growing areas,leading to food shortages.

请问 because 在这里有哪些用途？

Not only is smoking bad for your health,its the source of social problems in developing countries because, since profit from tobacco is very high, tobacco has taken up the best food-growing areas,leading to food shortages.

“because, since profit from tobacco is very high, tobacco has taken up the best food-growing areas,leading to food shortages.”是修饰its the source of social problems in developing countries是什么原因状语从句。该从句中的“since profit from tobacco is very high”为“tobacco has taken up the best food-growing areas”是什么原因状语从句。即because缘由状语从句本身又是一个带有缘由状语从句的主从复合句。