农业生产经营组织、农业机械所有人应当对（）及相关人员进行农业机械安全使用教育，提高其

请先阅读下面短文，掌握其大意，然后根据短文内容从下面方框内的七个选项中，选择五个还原到文中，使短文意思通顺、结构完整，并在答题卷上将其序号涂黑。(每小题2分)

Hi Grace,

How's it going? Sorry I haven't emailed for a while, but I had so much to do!

I had told you about my decision to take up a sport. I knew I wasn't fit and I wanted to get some exercise. But that wasn't the only reason that I decided to do a sport. Students who play sports do better at school. 小题1:                    Exercise also helps learning and memory (记忆).

 小题2:                 First, I tried soccer. I had played a bit of soccer before and I thought it wouldn't be too bad. I knew I couldn't nm for very long without feeling tired. On the first day, I was able to nm for the first ten minutes, but then I was so tired that I couldn't even kick the ball!

Then, I tried volleyball. 小题3:               I was able to run for the first twenty minutes and I wasn't the slowest runner in the team! After a few weeks .I could run faster and longer. I was doing better and feeling better. 小题4:            Maybe I'm not a team sport person after all!

Finally, I tried kung fu (功夫). It's a great sport that exercises the body and the mind. You learn to follow instructions carefully and do what you are asked to do. This is the right sport for me!  小题5:                 I feel so confident that l even showed some moves to the class last week! Can you believe it?

I hope you're OK! Write and let me know what you've been doing!

Bye for now!

Kristie

艾滋病患者在口腔可出现以下表现，除了

A．毛状白斑

B．坏死性龈炎

C．Kaposi肉瘤

D．Wegener肉芽肿

E．非霍奇金淋巴瘤

二次型

，经过正交变换化为标准形：

，
(1)求a，t的值．
(2)求所用的正交变换X=PY．

谈判沟通应掌握哪些原则？

打印机的种类很多，从印字原理上讲可分为（）和（）。其中击打式打印机主要以针式打印机为主，而（）、（）、（）、（）等打印机都是非击打式打印机。