阅读下面文言文，回答问题。

    连处士，应山人也。以一布衣终于家．而应山之人至今思之。其长老教其子弟，所以孝友、恭谨、礼让而温仁，必以处士为法，曰：“为人如连公足矣。”其矜寡、孤独、凶荒、饥馑之人皆曰：“自连公亡，使吾无所告依而生，以为恨。”呜呼!处士居应山，非有政令恩威以亲其人，而能使人如此，其所谓行之以躬，不言而信者欤!

    自其祖先裕尝为应山令，后为磁、郢二州推官，卒而反葬应山，遂家焉。处士父以疾废于家，处士供养左右十余年，因不复仕进。父卒，家故多资，悉散以赒①乡里，而教其二子以学，曰：“此吾资也。”岁饥，出谷万斛以粜②，而市谷之价卒不能增，及旁近县之民皆赖之。人有贫而窃其牛者，官捕之甚急，以牛自归。处士为之愧谢曰：“烦尔送牛。’’厚遗以遣之。

    处士有弟居云梦，往省之，得疾而卒，以其枢归应山。应山之人去县数十里迎哭，争负其柩以还，过县市，市人皆哭，为之罢市三日，曰：“当为连公行丧。”

【注释】①蜩(zhōu)：救济，接济。②粜(tiào)：卖出粮食。

    Top students always have special ways of learning that others probably can learn. Here are some of their secrets（秘密）.

    Study any time and everywhere. Some work late at night. Others work early in the morning. And some others study as soon as they come back home. All the ways are OK, but you should keep your own.

    Learn how to read. The secret of good reading is to be an active reader. Asking questions makes a full understanding of the book.

    Plan your time. If you want to be the top, make sure to finish all tasks on time.

    Keep your papers clean. Clean papers are likely（很可能的）to get higher grades than dirty ones.

    Top students often make up possible test questions（模拟测试） themselves. It helps them find exams much easier.

    Do more than what your teacher asks. The more you practice, the more you learn.

有同学在阅读《可爱的菏泽》一书时发现：宋朝以前，菏泽曾是经济最发达的地区之一，人才辈出；两宋以后，经济落后，杰出人物寥若寒星。导致这一变化的主要原因是（    ）

若集合$A=\{-2,-1,0,1,2\},B=\{1,0,2,3\}$ ，则$A\cap B=$（    ）