Which choice lists these species in order of gestation length, from longest to shortest pregnancy?

The correct answer is the one that accurately reflects the gestation lengths of the species listed in order from longest to shortest.

In general, horses have the longest gestation period among common domestic species. Horses typically have a gestation length of around 11 months (about 330-345 days). Cows follow, with a gestation period of approximately 9 months (around 280 days). Goats also have a similar gestation length to cows, around 150 days, which is shorter. Pigs tend to have a shorter gestation period of about 3 months, 3 weeks, and 3 days (approximately 114 days). Lastly, dogs have the shortest gestation period among these animals, approximately 63 days.

By this order, the sequence is: Horse (longest), Cow, Goat (similar length), Pig, and finally Dog (shortest). Thus, the choice that lists these animals in this correct descending order of gestation length is accurate. Other options either misplace the sequence or do not adhere to the established gestation lengths of these species.