What must be naturally attached to the major body part to prove the sex of a bull?

To determine the sex of a bull, the most reliable method is through the head with antlers. This is because male bulls typically possess antlers that develop as they mature, serving as a clear indicator of their sex. Antlers are not only a secondary sexual characteristic but also have specific growth patterns and shapes that are associated with male animals.

In addition to being a visual indicator of the bull's sex, antlers are involved in behaviors related to mating during the breeding season, further emphasizing their significance. The presence of developed antlers is a definitive sign that an animal is male, whereas the absence of antlers would suggest it is either a female or a juvenile male that has not yet developed them.

Other choices do not provide a definitive way to ascertain the sex of a bull. For example, hooves do not indicate sex, as both males and females have similar hoof structures. A tail also cannot distinguish between sexes, as both genders possess tails that are functionally similar. Fur provides no sexual differentiation, as its characteristics can vary widely among individual animals regardless of their sex. Therefore, the head with antlers stands out as the most definitive feature for determining the sex of a bull.