be careful when you are crossing the street.可以改写成be careful when crossing the street.

题目

be careful when you are crossing the street.可以改写成be careful when crossing the street.
when my mother saw that i was unhappy,mother called me to her bedroom.可以改写成seeing that i was unhappy ,mother called me to he bedroom.为什么第一句有when而第二句不用when?

答案

　　be careful when you are crossing the street,说话的对象应该是你,你们,所以可改写成be careful when crossing the street.
　　seeing that i was unhappy ,与后面的mother called me to her bedroom,这两个动作应该是同时发生的,seeing that i was unhappy 这里可理解为伴随状语.句子意思为：母亲见我不开心就把我叫到她的卧室去.