Which of the following animals has the longest gestation period?

The animal with the longest gestation period from the given options is the horse. Horses typically have a gestation period of about 11 months, which can range from approximately 320 to 380 days.

This extended gestation period is attributed to the developmental needs of a horse foal. Horses are large animals, and the longer gestation allows for the foal to grow adequately and be born at a size where it can stand and run shortly after birth, which is crucial for its survival in nature.

In comparison, cattle generally have a gestation period of around nine months, while sheep have an average of five months, and swine (pigs) have a gestation period of about three months, three weeks, and three days. The differences in gestation periods among these animals are largely due to their size, developmental requirements of the young, and evolutionary adaptations that have occurred over time.