Here are your corrections, Eric for your homework:

" Why we cannot pet lions, tigers and foxes?  "

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Because they are dangerous animals and fierce

> Because they are dangerous and fierce kind of animals.

* It is important to make the sentence clear and understandable.

All of them eat meat like dears, giraffes and pigs.

> This sentence is correct.

Also, they can eat people. Be careful.

>This sentences is correct.

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Good Job, Eric! 

        Your homework was very impressive. Keep up the good work and always make habit of reading English books. Take care. ^_^

See you in the class.

~T.Cassie