题干

下列属于特异性免疫的是( )

A:皮肤的屏障作用

B:患过麻疹的人不再患麻疹

C:白细胞的吞噬作用

D:溶菌酶的杀菌作用

上一题 下一题 0.0难度 选择题 更新时间:2018-12-13 08:12:14

答案(点此获取答案解析)

B

同类题2

阅读理解

    In Europe, small cars have always been more popular than large cars. In the United States, large cars and midsize cars are more popular than smaller cars. As a result, European automakers used to make different kinds of small cars while American automakers used to build bigger, heavier cars. However, these days, automakers in both America and Europe produce cars of different sizes. This is because most automakers export their cars all over the world.

    The price of gasoline (汽油)is one reason for differences in car choices. Since gasoline is more expensive in Europe, many Europeans want smaller, lighter cars that will travel a long way on a gallon(加仑)of gasoline.

    Other reasons also enter into the big or little car decision. Many European cities have narrow, winding(弯曲的) streets. In these cities a small car is easier to control than a large one.

    For a long time, few Americans bought small cars. Instead they chose large cars, because these roomy cars were more comfortable for large families and long trips. Some people also liked the powerful engines(发动机) that large cars had. Since gasoline was cheap, drivers did not mind that the large cars used a lot of gasoline.

    But in the 1970s, there were gasoline shortages in the United States. The price of gasoline went up. Though large cars were still more popular than smaller cars, sales of small cars increased. Some people also bought small cars because these cars caused less air pollution than larger cars.

    Today, Americans' car preferences are still changing. Though Americans are still buying many small cars, the fastest growing sales are for certain kinds of large cars. These types of cars are called minivans and sport utility vehicles(SUV). They are very popular today. But of course, that could change tomorrow.

同类题4

现代文阅读与探究。
                                                                                                       一只叫迈克的鸡蛋
                                                                                                               德里·莫里森
        ①抚养一个患自闭症的孩子不是件容易的事,这种特殊的经历,没有亲身感受的人很难理解。自从儿子马克西被确诊为自闭症以后,我的生活彻底改变了。起初我气愤、惶恐、抱怨命运不公。但渐渐地我学会了如何跟自闭症和平共处,甚至学会了如何享受这种生活。
         ②大约从4岁开始,马克西疯狂地爱上了鸡蛋——不是吃,而是玩。他喜欢把鸡蛋攥在手里,喜欢看它们在饭桌上打转,喜欢把它们捏碎让黏糊糊的液体流到手上、衣服上、地毯上。
         ③每次从超市购物回来,我都会把鸡蛋放在一个保密的地方。但跟其他自闭症的孩子一样,马克西非常聪明,他能撬开家里所有的锁,能找到任何被藏起来的东西。所以,就算家里只有一个鸡蛋,也难逃他的“魔爪”。
        ④每次看到马克西坐在地上,身边散落着鸡蛋壳,蛋清和蛋黄涂得满身满脸,我都想尖叫。可是儿子总会在这时抬起头,用一双清澈的眼睛看着我,自豪地向我展示手里的半枚鸡蛋黄。他那灿烂的笑容让我无法抗拒,除了哈哈大笑,我还能有什么选择呢?和生鸡蛋之间的战争,我似乎永远是战败方。
         ⑤有一次,我又买了一些鸡蛋,但并没有把它们藏起来,我决心尝试一个新策略。我把一个鸡蛋煮熟,然后在蛋壳上画了一张笑脸。“马克西,”我把熟鸡蛋递给儿子,“这是给你的。”小家伙狐疑地盯着我,看了又看,妈妈主动交出一个鸡蛋?这简直不可思议。马克西接过鸡蛋,虔诚地把它捧到客厅。我听到儿子低声地对鸡蛋说:“你好,迈克。”显然这是他给新朋友起的名字。要知道,这是马克西第一次开口说话——虽然对方是一只鸡蛋!你没法想象我当时有多激动。
        ⑥几分钟后,按捺不住好奇心,我蹑手蹑脚地走进客厅。儿子正在沙发上安静地看电视,鸡蛋迈克“坐”在他旁边的垫子上。“马克西,记住,”我郑重其事地说,“迈克是只鸡蛋,你要温柔地对待它,不能把它捏碎了。”没想到儿子竟跟着我重复道:“迈克,温柔。”出生后,这是他开口说的第二句话。
        ⑦直到那天晚上,迈克仍然毫发无损。但快睡觉的时候,马克西悄悄地溜进厨房,打开冰箱门。我的心收紧了,儿子又要开始摆弄生鸡蛋。看来这场跟鸡蛋的战争,失败的还是我!我气急败坏地冲进厨房,决心狠狠地教训儿子一顿。但眼前的一幕让我说不出话来。借着微弱的灯光,我看见他亲吻了一下迈克的“光头”,小声说:“晚安,迈克。”然后温柔地把它放进冰箱。那一刻,我比拿到诺贝尔奖还自豪。
        ⑧现在马克西已经5岁了,通过跟迈克的“交流”,儿子会说的单词越来越多了。最近,他甚至开始主动跟亲戚朋友打起招呼来。我和生鸡蛋的战争早已结束。不过,每隔几天,我还是会为儿子准备一只熟鸡蛋,一只叫迈克的鸡蛋。