空气的成分中,体积分数约占21%的气体是 A. 氮气         B. 氧

 空气的成分中,体积分数约占21%的气体是

A. 氮气         B. 氧气         C. 二氧化碳     D. 稀有气体

答案

B

相关题目

生长在沙漠中的仙人掌,其肉质茎的细胞中含量最多的化合
生长在沙漠中的仙人掌,其肉质茎的细胞中含量最多的化合物是( ) A.蛋白质          B.脂质        C.糖类     D.水  
 The problem ______ many children, especially girls, have ________ school is g
 The problem ______ many children, especially girls, have ________ school is getting more and more serious. A. which; got out of B. that, dropped out of C. that, fallen out of D. which, run out of
设F为抛物线y=-x2的焦点,与抛物线相切于点P(-4,-4)
设F为抛物线y=-x2的焦点,与抛物线相切于点P(-4,-4)的直线l与x轴的交点为Q,则∠PQF的值是       .
下列有关有机物的说法正确的是        A.蛋白质、淀粉
下列有关有机物的说法正确的是        A.蛋白质、淀粉、纤维素、蔗糖都属于有机高分子化合物        B.乙醇、乙酸、乙酸乙酯可以用饱和碳
—Do you still remember the first time we met, Linda?        —Sure. You
—Do you still remember the first time we met, Linda?        —Sure. You       a meeting in our classroom.        A.were addressing              B.had addressed  
Testing has replaced teaching in most public schools. Pretests, drills, tests, a
Testing has replaced teaching in most public schools. Pretests, drills, tests, and retests fill my own children’s school week. They know that the best way to read a textbook is to look at the questi
在同温同压下,下列各组热化学方程式中,的是 A.        
在同温同压下,下列各组热化学方程式中,的是 A.             B.                      C.                        D.       
全球变暖对局部地区能带来一些好处。下列叙述正确的是( 
全球变暖对局部地区能带来一些好处。下列叙述正确的是(    ) A.高纬度地区会变得适宜于温带作物分布 B.全球变暖,能源消耗总量减少 C.全球变暖

最新题目