α-丙氨酸是组成人体蛋白质的氨基酸之一，其分子结构如图所示。（注：“ ”表示氮原子；“ ”表示碳原子；“ ”表示氧原子；“ ”表示氢原子，“-”表示原子之间相互连接。）

则α-丙氨酸中含有____种元素，其中碳、氧2种元素质量比为____，其相对分子质量是____。

下列句子中不含通假字的一项是(    )。

如图甲所示，空间存在方向竖直向下的匀强磁场，MN、PQ是水平放置的平行长直导轨，其间距L=0.2m，连在导轨一端的电阻R=0.4Ω，ab是跨接在导轨上质量m=0.1kg的导体棒．从零时刻开始，对ab施加一个大小为F=0.45N，方向水平向左的恒定拉力，使其从静止开始沿导轨滑动，滑动过程中棒始终保持与导轨垂直且良好接触，图乙是棒的v﹣t图像，其中AO是图像在O点的切线，AB是图像的渐近线．除R以外，其余部分的电阻均不计．设滑动摩擦力等于最大静摩擦力．已知当棒的位移为10m时，其速度达到了最大速度10m/s．求：

   In many high schools，there are strict rules about using mobile phones. If your phone rings in class，for example，the teacher will be very angry.
   Every mobile phone has a ringtone (铃声). It tells you that someone is calling you. Now，there is a ringtone called “mosquitotone (蚊子铃声)”. Using it，students can receive calls and text messages (短信) in class but the teacher will not realize what is happening. How?
   Mosquitotone has a special sound. Only children and teenagers can hear it. As we get older，we are unable to hear some sounds with high frequencies (频率). As a result，a child or teenager can hear the mosquitotone ringtone, but it's_inaudible_to someone 20 or older.
   But sometimes，people over 20 can hear the ringtone. One British student's phone uses mosquitotone. In class，the student's phone rang. The 32­year­old teacher looked at the student and became unhappy. “I heard that. You know the rule：no mobile phone in class.”
   Not all the students are interested in mosquitotone. Jerry Jones，a high school student of 17，says，“Using mosquitotone too often is bad for our hearing. I may use it for pleasure，but not in class. It's unfair to the teachers！”
   What do parents think of mosquitotone？“I think it is perfect for places like movie theaters，” says Connie Neeson,44.“Think about it. Yon're watching a film and someone's mobile phone rings. Mosquitotone is good because many people don't hear it. However，it also has a bad influence on their study if students use it in class.”