It was really cold last winter.Really?I was in Sanya then.Yo

介词考点：
at和inat和in后街地点名次是,at后通常为相对较小的地点,in后通常为相对较大的地点。如：They arrived at our school yesterday。Our teachers arrived in Beijing this morningin,on和toin表示甲被包含在乙的范围内：on强调甲与乙接壤：to则常常指甲与乙互不包含,也不接壤。如：Dalian is in the north of China。Hubei is on the north of Hunan。Australia lies to the sourth of China。【这个就是你要找的考点Sanya是包含在中国的范围内的所以用in】

纯码字拜托采纳。