1.th不管是在前面后面,都可以正常写.
2.1号first
2号second
3号third
11号eleventh
12号twelfth
13号thirteenth
21号twenty-first
22号twenty-second
23号twenty-third
31号thirty-first
32号thirty-second
33号thirty-third
（从21开始,依此类推）
3.友情提醒8-eighth 9-ninth 12-twelfth 20-twentieth