it 用来指同一个物体.如：Your bag looks nice.Where did you buy IT?I want to buy one.“你的包真好看.你在哪买的它?我也想买一个.IT 指的前句中的Your bag.和Your bag是同一个物体.（one则指同一类物体）在比较句中如果是单数或不可数名词要用that 复数就要用those 如：The mooncakes from Guangdong are nicer than those from Beijing.