Mr.Jones and his wife （are） looking at them 和Sometimes he an

Mr.Jones and his wife （are） looking at them 和Sometimes he and his wife watch televsion.区别：Mr.Jones and his wife are looking at them 和Sometimes he and his wife watch televsion区别：为什么前面一句看要用系动词are,后一句却不用,但是我是一个人在家自学,所以对我来说理解起来比较困难!