题干

下图是测定空气中氧气含量的实验装置,(装置气密性良好),有关分析中正确的是(   )

A:进入集气瓶中的水约占烧杯中水的五分之一

B:燃烧匙中的药品可以是木炭

C:氮气不与红磷反应且难溶于水,是设计该实验的依据之一

D:燃烧停止后立即打开弹簧夹

上一题 下一题 0.0难度 选择题 更新时间:2014-07-08 06:09:18

答案(点此获取答案解析)

C

同类题2

   The teacher stood before his class and was going to hand out the final exam papers. “I know how  1   you have all worked to prepare for this test,” he said. “And because I know you can do it well, I am willing to offer a B to anyone who would  2  not to take the test. ”
   Many students jumped up to   3   the teacher and left the classroom.  The teacher looked at the   4  students and said, “Does anyone else want to get a B? This is your last   5 . ” Two more students decided to go.     Seven students remained.  The teacher then handed out the  6   .  There were only three sentences typed on the paper: Congratulations! You have just   7   an A in this class.  Keep believing in yourself.     I never had a teacher like that, but I think it is a test  8   any teacher could and should give.  Students who are not   9   in what they have learned are B students at best(充其量). The same is   10   in real life.  The A students are those who believe in what they are doing because they have   11   both successes and failures.  They have learned life’s lessons, either from normal education   12  from events in their lives, and have become   13   people.      Scientists say that by the age of eight, 80% of what we believe about ourselves has already been formed.  You are a big kid now, and you   14   that  you have some limits (限制).  However, there is   15   you can’t do or learn or be.  Sir Edmund Hillary, the first person to reach the summit of Mount Everest said, “It’s not the mountain we conquer(克服) but ourselves. ”