病毒在寄主细胞内的生命活动主要表现在（    ）

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．

关于桑椹胚和囊胚的比较,以下说法正确的是（   ）

阅读下列材料，回答问题
材料：秦王扫六合，虎视何雄哉！挥剑决浮云，诸侯尽西来。
                                                                                                                                                                                       ——李白《古风》
请回答：
（1）李白诗中的“秦王”叫什么名字？ “扫六合”指的什么事情？
（2）“扫六合”后，秦王称呼发生了什么变化？都城定在什么地方？ 
（3）“秦王扫六合”有什么样的历史意义？