已知a＞0，实数x，y满足：$\left\{\begin{array}{c}x\ge 1\\ x+y\le 3\\ y\ge a\left(x-3\right)\end{array}\right.$，若z=2x+y的最小值为1，则a=（　　）

根据下列句子及所给单词的首字母，在答题卷上按题号写出各单词的完全形式（每空限填一词）。
⑴My grandfather likes to water the f____  in the garden on weekends.
⑵The boy is too young. So don't leave him a____  at home.
⑶If I don't help my mom do some h____  on weekends, my mother will be very angry with me.
⑷Last night I didn't go to bed u____  the TV program was over.
⑸Last Sunday I w____  a letter to my father.
⑹I need to look smart for my job i____ .
⑺He f____  his test last week. He should study hard.
⑻He m____  his teacher in the street yesterday.
⑼When the little girl saw the big tiger, she felt very s____ .
⑽Last week, I p____  500 yuan for my new bike.

— Are there any boys in the classroom?

—        , they're in the lab.

十一届全国人大三次会议期间，共收到代表团和代表议案506件，收到全国人大代表提出的建议、批评和意见7 418件，在数量上，创历次会议新高；在内容上，涉及国民经济各个部门、社会活动各个领域、人民生活各个方面，反映了代表对解决好关系人民群众切身利益的重要问题的强烈期待；在质量上，许多建议经过深入调查研究，在广泛听取群众意见的基础上提出，具有较强的针对性和代表性。这表明(   )
①人大代表由人民选举产生
②人大代表代表人民的利益和意志
③人大代表的履职能力大大提高
④人大代表自觉接受人民监督

农业生产中人们常通过种植豆科植物来提高土壤肥力，因为豆科植物的根上长有____ ，其中生活着叫____ 的生物，它们能固定空气中的____ ，使土壤中的____ 元素含量增高，从而让植物生长旺盛．