请教英文句法问题
1.Music players cause a serious health problem, with teenagers as the most at-risk group.
"with teenagers..."这一部分是什么成分啊,其意思又是什么啊?
还有,是不是有problem with sb.这个用法啊?
2.One in four teens is in danger of early hearing loss as a direct result of bad listening habits,says Prof. Chava Muchnik.
这句话中,为什么是“says Prof..."而不是“said Prof..."呢.
谢谢!