2014 is the year of horse in China. Do you know anything about the horse? The horse is strong and runs very fast. He's a useful and hard-working animal. The horse learns to know his master  soon. He loves his master, even after his master has died. Here's a story about such a horse. In a war, the master was killed, and fell from his horse. When his body was found some days later, the horse was still standing beside it. During that long time, the horse didn't leave the body of his master, without food or water, in the coldest weather, driving away the birds that might eat it. Wasn't he a great animal? The story probably took place in   _  .
spring summer autumn winter