阅读下列材料,结合所学回答问题
材料 卫鞅曰：“治世不一道，便国不法古。故汤武不循古而王，夏殷不易礼而亡。反古者不可非，而循礼者不足多。”孝公曰：“善。”以卫鞅为左庶长，卒定变法之令。
——引自《史记·商君列传》
请回答：
（1）文中“卫鞅”指的是谁? 文中“孝公”是哪国国君? 他们是什么时期的人？
（2）文中的“变法之令”的主要内容有哪些？

（3）变法有什么作用？

数列{a_n}共有11项，a₁=0，a₁₁=4，且|a_k+1﹣a_k|=1（k=1，2，…，10），则满足该条件的不同数列的个数为（　　）

根据短文理解，选择正确答案。

    We're always looking for well­written reviews of books， music， movies， television shows， websites， video games and other products. When writing a review， concentrate on exactly what you liked or didn't like. Give examples of strengths and weaknesses，be descriptive and provide background information on an author，director，actor or musician，if possible. Find professional reviews in magazines or newspapers and see how reviewers deal with their topics，but be sure to express your own voice in your review.

    Grammar Hint for Reviews：When describing a book，movie， album or anything else，use the present tense.

Book Reviews

    Discuss an author's technique，strengths and weaknesses instead of focusing on the plot. Does the story flow？ Is there a strong sense of character and place？Did you stay up until dawn to finish it？Is it good reading for teenagers？What influence did it have on you and why？If you've read other books by the same author， discuss how this book compares.

Movie Reviews

    Think of the major Oscar categories and consider the performances， music， lighting and setting， etc. Do these work together？ Did some hold up while others didn't？ If the movie is based on a book， discuss whether one is better than the other and why. If the movie is a remake， compare the film to its original.

    Remember that a well­written movie review should discuss strengths and weaknesses. Some readers may not have seen a movie yet， so don't give away an exciting scene or the ending！

College Reviews

    Begin by providing an overview of the college，including location，size and a description of the campus and/or dorm life. Think about all aspects of your college visit. What academic，athletic and after­class programs are available？ What are the students like？ What makes the college different from others？ Every school has strengths and weaknesses. Be objective. Consider what the school has to offer and who might enjoy or benefit the most from attending there.

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