B

    As we all know，having a great memory is important．It can help you succeed in school，in your job，and in life．It also helps you learn faster and better．We all know that fast learner's are always in demand．If you have a great memory, I'm sure you can succeed more easily．

    If you are willing to make a few changes in your life．you should improve your memory first．My plan is to explain every skill that can help you improve your memory．

    You can not only learn memory skills on this website，but also learn how to improve your memory through diet，exercise，sleep and other ways．

    I think that memory improvement can be achieved (实现)in two ways：improving the health of your brain and using memory skills．Many people think they may be difficult．In fact, they are easier to do than you might think，but you have to work hard by yourself.

    Memory improvement needs time and effort on your part．You cannot improve your memory if you do not work on it．Of course，I believe that a more powerful brain is well worth the effort!

    Here are a few of the great memory improvement tips．I will give you some tips in the following part．

下列各句中，没有语病的一项是(　  　)

（2017•新课标Ⅱ）选修4-4：坐标系与参数方程选讲
在直角坐标系xOy中，以坐标原点为极点，x轴的正半轴为极轴建立极坐标系，曲线C₁的极坐标方程为ρcosθ=4．

（Ⅰ）M为曲线C₁上的动点，点P在线段OM上，且满足|OM|•|OP|=16，求点P的轨迹C₂的直角坐标方程；

（Ⅱ）设点A的极坐标为（2， $\frac{\pi }{3}$ ），点B在曲线C₂上，求△OAB面积的最大值．

（2016•山东）已知数列{a_n}的前n项和S_n=3n²+8n，{b_n}是等差数列，且a_n=b_n+b_n+1．

在下列横线上填上合适的词。

一____合唱队　 一____小黄莺

一____小朋友　  一____杜鹃花