问题
不定项选择题
镁和铝分别与等浓度、等体积的过量稀硫酸反应，产生气体的体积（V）与时间（t）关系如下图。反应中镁和铝的
A．物质的量之比为3：2
B．质量之比为3：2
C．摩尔质量之比为2：3
D．以上均不正确
答案
答案：A
搜题请搜索小程序“爱下问搜题”
镁和铝分别与等浓度、等体积的过量稀硫酸反应，产生气体的体积（V）与时间（t）关系如下图。反应中镁和铝的
A．物质的量之比为3：2
B．质量之比为3：2
C．摩尔质量之比为2：3
D．以上均不正确
答案：A
| 阅读理解 | |||
| Teeth are important. Strong, healthy teeth help you chew all kinds of foods that help you grow. They help you speak clearly. And yes, they help you look your best. Here are some tips for you to take care of your teeth.
| |||
| 1. How many times at least should we brush our teeth a day? | |||
| A. 1. B. 2. C. 3. D. 4. | |||
| 2. What is the major cause of tooth decay? | |||
| A. Not brushing teeth. B. Not changing toothbrushes. C. Eating sugar. D. Not flossing teeth. | |||
| 3. How often should we change our toothbrushes? | |||
| A. Never. B. Three times a month. C. Every three months. D. Every month. | |||
| 4. Which is the right way to take care of your teeth? | |||
| A. Only brush front teeth. B. Don't brush teeth before sleeping. C. Spend at most three minutes brushing teeth each time. D. Eat lots of fruit and vegetables and drink water instead of soda. |