these 是代词,意思是“这些” These flowers are beautiful.这些花很漂亮.they 人称代词,意思是“他们” My friends are playing football,and they want us to play too.我的朋友们在踢足球,他们想要我们也（一起）...they are my pencils.行吗？总觉得怪怪的语法上是没问题的。单独用是怪怪的，如果联系上下文就不会奇怪了。好吧