下列关于细胞结构与功能的描述，正确的是（　　）

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    “I don't feel right about this,” I said to one of my cousins in a low voice. She nodded in 1 . Not wanting to be the first to touch the food, I waited for one of the older adults to start.

    Thanksgiving usually meant 2  and full stomachs, however, this year was 3. My family sat around the dinner table 4 at our feast. Everyone had a full plate, everyone except for Grandma. The treatment for throat cancer would 5  one of her great pleasures, eating. This was the first 6of many food-focused 7  to come. I could not imagine what it would be like to never taste food again. My cousin Molly broke the 8 with a raise of her glass, “To Nat.” We all followed her lead. “Your 9 and strength encourage us all,” she continued. Grandma smiled, holding back her tears with great 10 . “Thank you. Please, please eat.” And with that, we all began to eat. Conversation broke 11around the room while Grandma laughed and talked with us all. Cancer would take away her ability to eat, but not the gift of being the best hostess. The evening went on as 12 Thanksgivings do. By the time the night was over, I felt 13 to my family than ever before. I learned that we gather together on holidays not to eat rich feast, but to 14 and share with one another. We 15 my Grandmother's courage, but we all learned a lesson in grace. In the years following, my Grandma 16 to create meals for family events. She told me once with a laugh, “I may not be able to eat, but I can 17 taste things.” With a 18 heart, Grandma prepared what she could not have for the only purpose of making us 19 . She inspired me to learn to cook and helped me find the 20 to make everything come together: love.

根据相关资料，回答下列各题。

材料  考古材料证明，玉米最早是在美洲培育出的。哥伦布将这种“奇异的谷物”带回欧洲后，在全世界得到迅速传播，成为世界三大谷物之一。到16世纪中叶，玉米被引入佛得角和西非，17世纪80年代在黄金海岸和达荷美之间的地区得到广泛种植，17世纪末18世纪初传入南欧地区。

16世纪中叶玉米传入中国，清嘉庆年间大面积种植，到鸦片战争前已在中国大部分地区引种而居杂粮之首。玉米等作物的引进与大面积种植，大大缓解了18世纪中叶到19世纪中叶中国因人口大幅度增长而带来的巨大粮食压力。

历史学家评述玉米在世界传播的意义时说，“其价值超过了所有的黄金”。

      (摘编自《通向现代世界的500年——哥伦布以来东西两半球汇合的世界影响》)

    When you cough or sneeze, you'd better turn your head away from others and cover your mouth with the full part of your hand. And then, you should say, "Excuse me."

    This seems so simple, but it is surprising how many kids have never been told to do this. Actually, I notice adults all the time who cough and sneeze in public without placing a hand over the mouth. One important thing I point out to the kids is that after they sneeze or cough on their hands, they should wash their hands as soon as possible. If not, they will be passing those germs (细菌) along to everything and everyone they touch.

    If you come to a door and someone is following you, hold the door. If the door opens by pulling, pull it open, stand to the side, and allow the other person to pass through first, then you can walk through. If the door opens by pushing, hold the door after you pass through.

    After a few weeks of seeing kids try to get through doors in the school and watching them enter restaurants as the door hit other people, I knew I had to discuss the problem with my students. Teaching them small acts of kindness, such as letting someone else go through a door first as they hold it open, may seem unimportant, but it can go along way toward helping students realize how to be polite and thank others. Once they've been told, they're halfway there.

    When we have to go up moving stairs, we will stand to the right. That will give others who are in a hurry a choice of walking up the left-hand side of the moving stairs. When we are going to enter a lift, the underground, or a doorway, we will wait for others to exit before we enter.

    After college when I moved to London, I was surprised at how polite everyone was in the subways. I was even more touched when I traveled to Japan. In both places, people made efforts to make way for others. On moving stairs, everyone stood to the right and walked to the left. On lifts, everyone would stand over to the side and allow others to exit before they would begin to enter.