例句：
1、He himself had only finished the fourth grade.
他自己只上完四年级。
2、What was that fourth priority, sir?
先后次序的第四条是什么，长官？
3、They hit pay dirt on the fourth day.
第四天，他们就发现了苗头。
4、A fourth model may be tested for flutter speed.
第四个模型可用来进行颤振试验。
5、Marry stood me up last night, and it was the fourth time.
玛丽昨夜又失约了，这已是第四次了。