A subject in grammar is the first part in a sentence about which the second part, the predicate, tells something.
There are many different types of animals there, each with its own purpose. Come and learn about why there are animals on farms, as well as specific facts about cows, chickens and pigs.
The answer is the first three. The speaker has a unique imagination so the answer is going to be directed towards the speaker. The first, second, and third answer directly acknowledges how the author sees things differently than everyone else. The other or last two options say what everyone else can see and is therefor not contributing to his imagination.
