21.The little boy won't go to sleep ________ his mother tells him a story.

　　A. or B. unless

　　C. but D. whether

　　[解析]句意：除非妈妈给他讲故事，否则小男孩就不去睡觉。or 或者，否则;unless 除非;but 但，除……之外;whether 是否。根据语境可知，这里用 unless 表示“除非……否则……”。

　　[答案]B

　　22.The school rules state that no child shall be allowed out of the school during the day, ________ accompanied by an adult.

　　A. once B. when

　　C. if D. unless

　　[解析]句意：学校制度规定：在白天，除非有大人陪同，否则不允许孩子走出校园。A：一旦;B：当……的时候;C：如果;D：除非。

　　[答案]D

　　23.________ you may have, you should gather your courage to face the challenge.

　　A. However a serious problem

　　B. What a serious problem

　　C. However serious a problem

　　D. What serious a problem

　　[解析]句意：无论你的问题有多严重，你都应该鼓起勇气来接受挑战。分析题干可知逗号前是让步状语从句，what 不能用来引导状语从句，所以排除B、D两项;however+adj.+a/an+单数名词=whatever+a/an+adj.+单数名词，故C项正确。

　　[答案]C

　　24.________ our manager objects to Tom's joining the club, we shall accept him as a member.

　　A. Until B. Unless

　　C. If D. After

　　[解析]句意：我们愿意接受汤姆为我们的成员，除非经理反对他加入本俱乐部。选项中的四个词都可以连接从句。但是这里存在条件关系，故排除A(直到)和D(在……之后)，而语境存在否定条件，故排除C(如果)。

　　[答案]B

　　25._______ they decide which college to go to, students should research the admission procedures.

　　A. As B. While

　　C. Until D. Once

　　[解析]句意：一旦学生们决定了要上哪所大学，他们就应该研究申请此大学的程序了。as 当……时，由于;while 当……时，尽管;until 直到;once 一旦。根据句意选择D项。

　　[答案]D

　　26.John thinks it won't be long ________ he is ready for his new job.

　　A. when　　　B. after C. before　　　D. since

　　[解析]句意：约翰认为不久他就能为他的新工作做好准备。本题考查句式 It won't be long before...，表示“过不了多久就……”。注意以下句子的区别：

　　①It is three years since he left.

　　②It was three years before he left.

　　③It was three years ago that he left.

　　④It was three o'clock when/before he left.

　　[答案] C

　　27.—Our holiday cost a lot of money.

　　—Did it? Well, that doesn't matter ________ you enjoyed yourselves.

　　A. as long as B. unless

　　C. as soon as D. though

　　[解析]句意：——我们这次度假花了很多钱。——是吗?没关系，只要你们玩得高兴就行。本题考查连词的用法。as long as 只要;unless 除非;as soon as 一……就;though 尽管，虽然。

　　[答案]A

　　28.The girl had hardly rung the bell ________ the door was opened suddenly, and her friend rushed out to greet her.

　　A. before B. until

　　C. as D. since

　　[解析]句意：这个女孩刚一按门铃，门就突然打开了，她的朋友冲出来迎接她。本题考查固定句型 hardly... when/before...，意为“一……就……”。

　　[答案]A

　　29.The engineers are so busy that they have zero time for outdoor sports activities, ________ they have the interest.

　　A. wherever B. whenever

　　C. even if D. as if

　　[解析]句意：工程师们如此忙碌，以至于没时间做户外活动，即使他们对做户外活动很感兴趣。本题考查连词。even if 即使，引导让步状语从句。wherever 无论什么地方;whenever 无论什么时候;as if 好像。

　　[答案]C

　　30.Just use this room for the time being, and we'll offer you a larger one ________ it becomes available.

　　A. as soon as B. unless

　　C. as far as D. until

　　[解析]句意：暂时用这个房间吧，一有可能，我们就会给你提供一个大点的房子。本题考查连词。as soon as 一……就……，引导时间状语从句。unless 除非;as far as 远到，至于;until 直到。

　　[答案]A

　　31.The old man asked Lucy to move to another chair ________ he wanted to sit next to his wife.

　　A. although B. unless

　　C. because D. if

　　[解析]句意：那位老人请 Lucy 换坐另一把椅子，因为他想挨着他妻子坐。本题考查状语从句引导词。由句意分析前后为因果关系，所以选 because。A尽管;B除非;C因为;D如果。

　　[答案]C

　　32.The little girl who got lost decided to remain ________ she was and wait for her mother.

　　A. where B. what

　　C. how D. who

　　[解析]句意：那个迷路的小女孩决定待在原地等她的母亲。where 引导地点状语从句。

　　[答案]A

　　33.—Shall we have our picnic tomorrow?

　　—________ it doesn't rain.

　　A. Until B. While

　　C. Once D. If

　　[解析]句意：——明天我们去野餐好吗?——如果不下雨的话。until 直到……时间;while 当……的时候;once 一旦……(就……);if 如果……

　　[答案]D

　　34.My parents don't mind what job I do ______ I am happy.

　　A. even though B. as soon as

　　C. as long as D. as though

　　[解析]句意：我的父母不在乎我从事什么样的工作，只要我高兴就好。本题考查状语从句。as long as(=so long as)引导条件状语从句，意为“只要”。as soon as 一……就……;even though 虽然，尽管;as though 好像。

　　[答案]C