题干

设数列为等差数列,其前n项和为,已知,若对任意都有成立,则k的值为(  )

A:22

B:21

C:20

D:19

上一题 下一题 0.0难度 选择题 更新时间:2019-07-02 06:23:08

答案(点此获取答案解析)

C

同类题2

阅读下面的文言文,完成下列各题。

    崔郾,字广略,姿仪伟秀,人望而慕之,然不可狎也。中进士第,补集贤校书郎,累迁吏部员外郎,下不敢欺。每拟吏,亲挟格,褒黜必当,寒远无留才。三迁谏议大夫。穆宗立,荒于游畋,内酣荡,昕曙不能朝。郾进曰:“十一圣之功德,四海之大,万国之众,其治其乱,系于陛下。自山以东百城,地千里,昨日得之,今日失之。西望戎垒,距宗庙十舍,百姓憔悴,畜积无有。愿陛下亲政事以幸天下。”帝动容慰谢,迁给事中。敬宗嗣位,拜翰林侍讲学士,旋进中书舍人,谢曰:“陛下使臣侍讲,历半岁,不一问经义。臣无功,不足副厚恩。”帝惭曰:“朕少间当请益。”高釴适在旁,因言:“陛下乐善而无所咨询,天下之人不知有向儒意。”帝重咎谢,咸赐锦、币。郾与高重类《六经》要言为十篇,上之,以便观省。迁礼部侍郎,出为虢州观察使。先是,上供财乏,则夺吏奉助输,岁率八十万。郾曰:“吏不能赡私,安暇恤民?”即以府常费代之。又诏赋粟输太仓者,岁数万石,民困于输,则又辇而致之河。郾乃旁流为大敖受粟,窦而注诸艚。民悦,忘输之劳。改鄂、岳等州观察使。自蔡人叛,鄂、岳常苦兵,江湖盗贼显行。郾修治铠仗,造蒙冲,驶追穷蹑,上下千里,岁中悉捕平。又观察浙西,迁检校礼部尚书,卒于官。吏部尚书,谥曰德。郾不藏赀,有辄周给亲旧,为治其昏丧。居家怡然,不训子弟,子弟自化。室处庳漏,无步庑,至霖淖,则客盖而屐以就外位。治虢以宽,经月不笞一人。及莅鄂,则严法峻诛,一不贷。或问其故曰陕土瘠而民劳吾抚之不暇犹恐其扰鄂土沃民剽杂以夷俗非用威莫能治政所以贵知变者也闻者服焉。

(节选自《新唐书•崔邠传》)

【注】①十一圣:穆宗之前的十一个皇帝。②敖:通“廒”,储存粮食的仓库。

同类题3

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

★  Many children like to eat snacks ineveryday life, and some of them even have snacks during dinner. To maintain thenormal meals and stay healthy, it is necessary to regularly eat snacks forchildren in their spare time.____

★Prepare healthy snacks in advance. When you make somethingyourself,youget to control the ingredients(原料)and put in what's good for you! You can also keep plenty of fresh fruit andvegetables at home to take on the go.____Keep the servings in bags in the fridge, ready to grab and go.

____

Makeit a habit to store some fruit, whole­grain crackers, or baby carrots in yourbackpack so you always have some healthy food nearby. Half a cheese sandwichalso makes a great snack to have on standby (备用).

★  ____

Healthysnacking doesn't have to be boring as long as you give yourself a variety ofchoices.

Whole­wheatbiscuits with peanut butter or low­fat fruit yogurt are healthy, tasty, andeasy.

★Satisfy cravings (渴望)with healthier approaches.

____ An 8­ounce mug of hot chocolate has only 140calories and 3 grams of fat. A chocolate bar, on the other hand, has 230calories and 13 grams of fat.

Eveningscan be a tempting time to have sugary, fatty snacks. If you're really feelinghungry, don't ignore it. Instead, pick the right snacks to fill the hunger gap.Whole­wheat bread, rice cakes, or popcorn can do the trick, so can fruit pairedwith cheese or yogurt.

A.Make it interesting.

B.Keep healthy snacks with you.

C.Read serving size information.

D.Cut up melons or vegetables inadvance.

E.Here are some ways to make healthysnacking part of your daily routine.

F.If you like to do some cooking aboutsnacks, you can follow the following ways.

G.If you're crazy for chocolate, try ahot chocolate drink instead of a chocolate bar.