Animal offspring often have unique names in English rather than simply being called "baby" plus the animal name, and this question checks knowledge of that specific vocabulary set. A young deer, still small and often spotted, is known as a "fawn."
Looking at the distractors helps confirm this. A "foal" is the young of a horse or a donkey, an animal with entirely different features and habitat from a deer. A "calf" belongs to a group of animals including cattle, elephants, and whales, again unrelated to deer despite all being mammals. "Joe" is likely a shortened or misspelled version of "joey," the correct term for a baby kangaroo found in Australia, not for a deer.
Since none of these other terms apply to deer, the only accurate answer is "fawn," confirming option 2 as correct.