亲爱的朋友们，这里晨间“话说地道美语”的答疑解惑课堂，我是Juliet。欢迎您的到来。今天我们将继续对第17课的功课进行解析并且做些知识拓展。

【习题解析】
第四题：这个足球队有一种新的踢法，他们保留这一手以便在重要比赛中出奇制胜。The football team has a new play they are keeping an ace in the hole the big game. 参考答案如下：that，as，for。完整句子为：The football team has a new play that they are keeping as an ace in the hole for the big game. 要完成这道题注意一下三个要点。

【要点详解】
第一、掌握定语从句。The football team has a new play that they are keeping as an ace in the hole for the big game. 这个句子是含有一个定语从句的复合句。主句是the football team has a new play，从句是由that引导的they are keeping as an ace in the hole for the big game。这个句子中的先行词是paly，它在定语从句中做keep的宾语，即：They are keeping the new play as an ace in the hole for the big game. 那么先行词是物，在定语从句中又做宾语，我们就要选择关系代词。指代物的关系代词有2个：which, that。由于先行词play在本句中是作宾语，则只能用that，不能用which。其实，that在这个句子中是可以省略的。

第二、掌握用keep来表述“把...留作”“把...当做”的短语是keep...as。那么短语中的as有的语法专家是说是引词，但是有的语法专家说是介词。我们来看2个例句：Which animal would you like to keep as a pet?你想养什么动物做宠物？My hopes. Is there any help to keep it as my daily goal? 我对未来抱有希望。我把它作为每日的目标是否有帮助？

第三、理解介词for是“用途”的意思。例如：It is a book for children. 这本书是儿童读物。We got a new table for the dining room. 我们买了张新桌子用于饭厅的。

【翻译习题参考答案】
1. 你的竞争者不知道你会有这样有用的办法。
Your competitors do not know that you have an ace in the hole.
2. 那律师手中的一张王牌是目击那次事件的一个秘密证人。
The lawyer's ace in the hole was a secret witness who had seen the accident.
3. 后备箱里那罐剩余的汽油是我们最后的王牌。
That spare can of gas in the trunk was our ace in the hole.

亲爱的朋友们，第17课的学习就全部结束了。下期我们将开始新一课的学习，精彩等着您。敬请关注下期晨间“话说地道美语”课程。希望这三期的习题解析能给您带来一点启发或者收获，哪怕您得以小小的启发或者是收获就是我的快乐。Thank you! Listeners, see you!