直线$x-y=2$被圆$(x-4{)}^2+y^2=4$所截得的弦长为（    ）

图示法是表示概念关系的直观方法，下列各项概念之间关系与如图所示概念关系相同的是（    ）

阅读下列短文，从每题所给的四个选项（A, B, C和D）中．选出最佳选项.

    What's your opinion on spicy food? Some people cannot handle even the smallest amount of chili(辣椒) in their dinner while others can't get enough of it.       

Scientists have long been puzzled by why some people love chili and others loathe it. Plenty of research has been done on the subject, dating back to as far as the 1970s. Previous results showed that a love of chili is related to childhood experiences, and cultural influences affect our taste buds, too. But the latest study has found that a person's love of spicy food may be linked to his or her personality more than anything else, CBC News reported.

     “We have always assumed that liking drives intake---we eat what we like and we like what we eat. But no one has actually directly bothered to connect these personality traits with intake of chili peppers,” said Professor John Hayes from Pennsylvania State University, who led the study.       

But before you look at the study, you should first know that “spicy” is not a taste, unlike sour, sweet, bitter and salty. It is, in fact, a burning sensation that you feel on the surface of your tongue. This got scientists thinking that maybe a love of spicy food is brought about by people's longing for thrill, something they usually get from watching action movies or riding a roller coaster.

In the study, 97 participants, both male and female, were asked to fill out questionnaires about certain traits of their personality, for example. Whether they like new experiences or tend to avoid risks. They were then given cups of water with capsaicin(辣椒素), the plant chemical that makes chili burn, mixed into them.

By comparing the answers to questionnaires and what participants said they felt about the spicy water. Researchers found that those who most tended to enjoy action movies or take risks were about six times more likely to enjoy the spicy water.

    Interestingly, we used to believe that the reason some people can withstand spicy food is that their tongue have become less sensitive to it. However, this latest study has found otherwise. It's not that it doesn't burn as badly, it's that you actually learn to like the burn,” Hayes explained.  

年三十的私房菜

    付春从城里回家时，爹和妈正在院子里剥玉米棒子。他们都没有发现身后的儿子付春。付春一声不吭地跨进院门，拎着大包小包进了自己的屋，放下行李，就一头栽倒在床上。爹和妈同时停止了手上的动作。时间静止了两分钟后，付春透过掉了半块的玻璃窗听见爹说，“春，回来了？”妈马上站起身来，责怪爹说，“他爹，春都进屋了，还问？快去抱柴火，我给儿子做吃的去。”付春拉起被角，捂在脸上，眼泪无声地流下。

    付春在城里一家五星级酒店当厨师。付春的厨艺好，在这家酒店一干就是五年，五年间付春很少回乡下，五年的城市生活让他下意识里已经把自己当成了城里人，他甚至发誓要在这家酒店干一辈子。然而，没想到这家酒店自从去年易主后，因经营不善，一天比一天不景气，上个月彻底宣告破产。

    失业这个月，付春把城里所有的饭店、酒店都找遍了，没有一个地方能容纳他。一些有名气的饭店、酒店，都有自己稳定的厨师团队，就算人家缺人手，他进去也只能是个打杂的。太小的饭店，薪水太低，高不成，低不就，就把付春挤回乡下的家了。付春感觉自己一下子从繁花似锦的春天走进了寒风凌厉的冬天。付春想着想着睡着了。

    “ 春，快起来吃饭了。”妈站在窗外，小心翼翼地喊付春，生怕声音大了，把儿子吓不见了似的，儿子已经有很久没回家了。

    饭桌上的菜，都是付春打小就爱吃的菜：干椒炒青菜、韭菜炒鸡蛋、火腿末炝嫩玉米，汤是酸菜土豆汤，酸菜是妈自己腌的乡下常见的老酸菜。旁边是一锅刚焖好的玉米饭。这些上不了台面的饭菜，也只有在家里才能吃到，虽说都是些在付春看来上不了台面的菜，但味道却是出奇的好。

    付春很快就风卷残云般把桌子上的饭菜一扫而光。爹和妈几乎一筷子未动，看着狼吞虎咽的付春，笑得嘴都合不拢。付春看着爹妈，抹着嘴回味着刚才的饭菜香味儿，突然脑子里像打开了一道尘封已久的门，付春兴奋地一连说了好几声：“我怎么没想到呢？”爹和妈被付春整糊涂了，还没回过神来，付春已经拎着大包小包跑出院门了。爹和妈赶紧跟到院门外，说：“春，你这刚回来，又要去哪儿啊？”“回城里。”付春头也不回地说。

    付春有足够信心让自己成为城里人，他不再怕失业，这一切都源于妈做的饭菜。付春在吃了妈做的菜后，突然想到了时下城里流行的私房菜。他想，现在城里人吃饭店都吃腻了，我何不当一名专做私房菜的厨师呢？

    很快，付春的私房菜就在城里闯出了名气，很多有钱人、领导都请付春到家里专门为他们做私房菜。尤其是每年的春节，付春更是分身无术。

    付春不断创新他的私房菜，几年后名声越来越大，钱也挣下不少，还在城里买了房子，拥有了城市户口。爹和妈不愿和他来城里，一直住在乡下的小土院，付春已经有好几个春节没回家陪父母过年了。每次爹妈打电话来，要他回家过年，付春都推托了。

    今年年三十那天，有个搞建筑的大老板，给了付春很多钱，说是特意请付春去为他父母做一顿年夜饭。这位老板的爹妈一直住在乡下，老板有心想接爹妈去城里过年，也享享福，可是爹妈不来城里，老板只好回乡下陪父母过年。老板和爹妈说回去过年，两位老人又忙里忙外辛苦做饭菜，因此老板骗父母不回家过年，请付春去做私房菜的目的是想让父母过个不用操劳的年。

    付春满口答应了，天快擦黑时，和老板一起赶到了老板乡下的父母家。没想到，他们推开门，首先映入眼前的竟然是一大桌子已经做好的饭菜，碗筷已摆好，就好像专等老板一到就开席似的。老板惊讶得合不拢嘴，不停地问两老怎么知道他要回来？

    老板的爹说：“每年不管你回不回家过年，你妈都会把饭菜做好，万一你回家了，也好吃上一口热乎饭。”老板的妈接着说：“这些都是你打小就爱吃的饭菜，在外面哪能吃到呢？”老板两眼含着泪，一把抱住了两位老人。

    一直站在门口的付春看着这一家子，缓缓地掏出钱包，把钱悄悄地放在门边的桌上，轻轻地合上门，头也不回地离去了。绚丽的烟花爆竹在付春身后、头上此起彼伏地响着、盛开着。付春仿佛闻到了妈做的干椒炒青菜、韭菜炒鸡蛋、火腿末炝嫩玉米，还有酸菜土豆汤的味道。

（选自《四川文学》，有删改）