六种短周期元素A、B、C、D、E、F的原子序数依次增大，其中A与E同主族，B与F同主族，E与F同周期。已知常温下单质A与E的状态不同，D的核电荷数是B的最外层电子数2倍，单质F是一种重要的半导体材料。则下列推断中正确的是 [ ]
A．由A、C、D三种元素组成的化合物一定是共价化合物
B．F与D形成的化合物性质很不活泼，不与任何酸反应
C．原子半径由大到小的顺序是：E>F>C>D
D．元素的非金属性由强到弱的顺序是：D>C>F>B
答案：C
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| What I Want for You and Every Child in America Dear Malia and Sasha, I know that you've both had a lot of 1 these last two years on the campaign trail, going to picnics and parades and state fairs, eating all sorts of junk food your mother and I probably shouldn't have let you have.But I also know that it hasn't always been easy for you and Mom, and that as excited as you both are about that new puppy, it doesn't 2 for all the time we've been apart.I know 3 I've missed these past two years, and today I want to tell you a little more about why I decided to take our family on this journey. When I was a young man, I thought life was all about me-about how I'd 4 my way in the world, become successful, and get the things I want.But then the two of you came into my 5 with all your curiosity and mischief (捣乱) and those smiles that never 6 to fill my heart and light up my day. I want all our children to go to schools 7 of their potential-schools that challenge them, inspire them, and instill (灌输) in them a sense of 8 about the world around them.I want them to have the chance to go to college 9 their parents aren't rich.And I want them to get good jobs: jobs that pay well and give them benefits like health care, jobs that let them spend time with their own 10 and retire with dignity. I want us to 11 the boundaries of discovery so that you'll live to see new technologies and inventions that improve our lives and make our planet cleaner and safer.And I want us to push our own human boundaries to reach 12 the divides of race and region, gender and religion that 13 us from seeing the best in each other. That was the 14 your grandmother tried to teach me when I was your age, reading me the opening lines of the Declaration of Independence and telling me about the men and women who marched for 15 because they believed those words put to paper two centuries ago should mean 16 . She helped me understand that America is great not because it is perfect but because it can always be made better and that the 17 work of perfecting our union falls to each of us.It's a charge we pass on to our children, coming closer with each new generation to 18 we know America should be. These are the things I want for you, to 19 in a world with no limits on your dreams and no achievements beyond your reach.And I want every child to have the same chances to learn and dream and grow and thrive that you girls have.That's why I've taken our family on this great adventure. I am so proud of both of you.I love you 20 you can ever know.And I am grateful every day for your patience, poise (自信), grace, and humor as we prepare to start our new life together in the White House. Love, Dad | ||||
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