初级英语语法.

如果有are后面就是watching了

这句是一般现在时的句子所以不用现在进行时

he and his wife是两个人，复数，所以动词用原形的

这段话是一般现在时，表示这些人平常都做些什么。第三人称单数就用watches, he and his wife是2个人，用动词原形即可watch

如果用 are watching 就是正在进行时，表示正在干什么事情

没有一种时态是可以用are watch组合的

be后面要加动词ing形式,构成现在进行时或将来时.
如果要用are的话,but sometimes he and his wife are watch television.是错的,应该写成but sometimes he and his wife are watching television.

不过一般来说,有了sometimes这样的词,一般不用现在进行时或将来时.

而像这样but sometimes he and his wife watch television.是一般现在时.

因为watch是个实意动词.在这边用一般现在时是不需要加are的.