必须用三单形式啊a cow eats grass祝你学习进步O(∩_∩)O哈!如果对你有所帮助,还望采纳O(∩_∩)O哈!如还有不懂的,还可以继续追问哦\(^o^)/~
cow不能直接用a来修饰,一头牛应该是a head of cow ,另外要用eats即三单形式。
it's eats not eat,you should try to check ur answer
A cow is eating grass.
时态是什么