台湾籍旅美老师今天交给我们的句子是：

There are many factors that can change the pigment of your hair, both internal and external. Things such as genetics, hormones, age, the climate that you live in, toxins and even chemical exposure can all affect hair pigmentation.
改变头发色素的原因有很多，包含内在因素和外在因素。像是基因、贺尔蒙、年龄、你居住地的气候、毒素、甚至是暴露在化学因子下，都可以影响头发的颜色。