Veterinarians help some sick animals. When animals need medicine, veterinarians prescribe medicine to them. Sometimes, they perform a = perform an operation. Veterinarians are not important to the people only. They are important to the animals too because they help some sick animals. I envy veterinarians because the = they can touch animals all the time. But I think they may be tired as they need to study medicine hard and take care of animals well.

I love how clearly you've presented your ideas. Fantastic effort! In addition, when a word starts with a vowel letter, the article you should use is "an". Thank you very much for doing your homework!