question:  What does the narrator say is significant about horses?
context: I The horses and packs were loaded before we went aboard the scoutship. Either your arches and calves ache or every time you step you think you're going to trip on a piece of fluff and break your neck. We have a place in the Ship like that—the Third Level—but it's only a thousand square miles and any time it gets on your nerves you can go up a level or down a level and be back in civilization. They don't care what order you go in, so Jimmy D. jumped up, grabbed his gear and then led his horse down the ramp. It means that everybody on the Ship is a person who can take care of himself if he has to. Daddy says that something has to be done in a closed society to keep the population from decaying mentally and physically, and this is it. I began to check my gear out—sonic pistol, pickup signal so I could be found at the end of the month, saddle and cinches, food and clothes. At our next landing, I grabbed Ninc's reins and cut Venie out smoothly. And I've seen things that looked good that I couldn't keep on my stomach. One of the smartest moves in history was to include horses when they dropped the colonies. Considering how short a time it was in which the colonies were established, there was not time to set up industry, so they had to have draft animals. One of the eight, as well as the two that were being built then, went up with everything else in the Solar System in 2041. I don't know how many of those planets had animals that could have been substituted but, even if they had, they would have had to be domesticated from scratch. I rounded a tree-lined bend, ducking an overhanging branch, and pulled Ninc to a stop. One of them had a string of packhorses on a line and he saw me and called to another who seemed to be the leader. That one wheeled his black horse and rode back toward me.
output:  Horses are the reason for the colonies’ success.
options:  Horses are a nuisance and make it hard for both colonists and scouts to get their jobs done.  Horses make it easy for criminals to conduct their business planet to planet .  Horses are the reason for the colonies’ success.  Horses are the reason for the catastrophe suffered on Earth.