同学你好，该知识点来自沪江网校《大学水平直达CATTI笔译三级丨随到随学班》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好
the phubbers have become a common sight in the cities, tied to their phones all the time
这里tied to their phones的逻辑主语是the phubbers，即the phubbers are tied to their phones all the time；

如果说“in the cities, which has kept their phones all the time，定语从句和中心词phubbers隔得比较远，可能会引起歧义；另外还要注意一下应该是have kept~
可以改成：the phubbers have become a common sight in the cities. They are keeping their phones all the time.
希望对同学有帮助~