A Bull And A Cow Is Grazing In The Field - Funny School Jokes

Can you correct this sentence ? What's wrong with it. Read it for funny answer.

Teacher : Correct the sentence,"A bull and a cow is grazing in the field."
Student : "A cow and a bull is grazing in the field."
Teacher : How?
Student : Ladies first.

Can you correct this sentence ? What's wrong with it. Read it for funny answer.
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