For professional athletes, ________ to the Olympics means that they have a chance to enter the history books.

如图所示的电路中，电压表所用的量程不明，当电路闭合后，V₁和V₂的示数分别如图所示．则V₁用的读数是____V，V₂用的读数是 ____V，小灯泡L₁上的电压是____V．

有机物A是烃的含氧衍生物，在同温同压下，A蒸气对乙醇蒸气的相对密度是2，13.8gA完全燃烧后，若将燃烧的产物通过碱石灰，碱石灰的质量会增加30.6g；若将燃烧产物通过浓硫酸，浓硫酸的质量会增加10.8g．若将13.8gA与足量金属钠充分反应，所得氢气的体积为5.04L（标准状况）．通过计算确定A的相对分子质量、分子式及结构简式．

阅读下列短文，从下面每小题的A、B、C、D四个选项中选出最佳选项。

B

    A group of children meet in the library each week during lunchtime. They are famous as the Miss Margaret Fan Club. Every Thursday, the twelve members of the Miss Margaret Fan Club make their way to the study center in the back of the library.
    The first Thursday they met, Miss Margaret greeted them with a little talk.
    "Welcome to the first meeting of the writing club!" she said. "During the school year, we will meet here to work on story writing. At the end of the year, I will put all of your stories together in a book."
    Miss Margaret gave a pencil and two pieces of paper to each student.
    "Now, your first homework is to think of a character. Now, try to think about an interesting person. When you think of this person, write down all the details(细节)about him or her in your head. "

鸟类适应飞行生活的特征不包括（  ）