帮我看看这句话有没有错,

问题描述:

帮我看看这句话有没有错,
since she hasn't received any letter from her son for three months,she is deeply concerned about his safety.
一句话中可以同时有since 和

没有问题.
如果since 是充当因为,而for 是 for three months ,完全没问题.
但是因为for 也有因为的意思,都党因为的话 他们两个就不能同时出现了.