在${\left(1-x\right)}^3{\left(1+x\right)}^8$的展开式中，含$x^2$项的系数是$n$，若${\left(8-nx\right)}^n=a_0+a_{1}x+a_2{x}^2+\cdots +a_n{x}^n$，则$a_0+a_1+a_2+\cdots +a_n=$ （  ）

    In America, drivers' education is part of the regular high school curriculum. Every student in his or her second year of high school is required to take a class in driver's education. However, unlike other courses, it is not given during the regular school year. Instead it is a summer course.

    The course is divided into two parts: class time for learning laws and rules and driving time to practice driving. Class time is not unlike any other class. The students study the basic traffic laws from a text to pass the written driving test that is given to anyone who wants to get a driver's license.

    Driving time is a chance for the students to get behind the wheel and practice starting. Each student is required to drive a total of six hours. The students are divided into groups of four. The students and the instructor go out driving for two hours each time. So each student gets half an hour driving time per outing.

    Drivers Ed cars are unlike other cars in which they have two sets of brakes(刹车), one on the driver's side and one on the other side where the instructor sits. So if the student driver should run into difficulties, the instructor can take over. The car also has another special feature. On the top of the car is a sign that reads: STUDENT DRIVER. That lets nearby drivers know that they should use extra caution because the student driver is a beginning driver, not very experienced.

    After the student has passed the driver's education course and reached the suitable age to drive (this age differs in every state but in most cases the person must be 16 years old), they can go to a the state office to take their driver's test, which is made up of an eye examination, a written test, and a road test. The person must pass all the three tests in order to be given a driver's license.

2016年1月21日，中国******在阿拉伯国家联盟总部演讲时指出，“我们在中东不找代理人，而是劝和促谈；不搞势力范围，而是推动大家一起加入‘一带一路’朋友圈；不谋求填补‘真空’，而是编织互利共赢的合作伙伴网络、”这表明（　　）

①中国坚持独立自主，走和平发展的道路

②我国外交政策的宗旨是维护世界和平、促进共同发展

③中国是维护世界和平与稳定的决定力量

④中国与中东各国在根本利益上存在着广泛的一致性

先化简，再求值
$\frac{2}{a-1}$＋$\frac{a^2-4a+4}{a^2-1}$·$\frac{a+1}{a-2}$，其中$a=\sqrt{2}+1$