题干

用已知物质的量浓度的NaOH溶液测定未知物质的量浓度的盐酸,在其它操作正确规范的前提下,下列操作一定会使测定结果偏高的是

A:酸式滴定管未用待测盐酸润洗

B:碱式滴定管未用标准碱液润洗

C:滴定过程中不慎有液体溅出

D:滴定前仰视读数,滴定后平视读数

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答案(点此获取答案解析)

B

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Many people run for exercise. But what will you do if you are not a “born” runner or jogger (慢跑者)? You may still want a kind of exercise that's inexpensive and easy to do. Why not try walking?

Walking requires no special equipment (装备). It is a kind of exercise that almost any normal, healthy person can do. Walking is good for your health like jogging or running; it will just take longer. Jogging and running make your heart work harder than walking. They also put more stress on your legs and feet than walking does.

    The problem with walking is that most people don't take it seriously. But there's a big difference between serious walking and the walking that most of us do. Walking, like jogging, should have a steady and continuous motion (稳健而持续的动作).

If you want to get your exercise by walking, you need to have your own walking plan. After all, runners and joggers set goals for themselves. Walkers need goals, too. You also need to set a course to walk. Start by walking about 15-30 minutes a day. Increase your time and distance (距离) slowly. And try increasing your walking speed little by little.

If you prefer to jog or run, follow the same advice. Start off slowly. Spend most of the first few days just walking. Then, start walking and running on the same day. Run or jog a short distance, then walk for a while, then, run, then walk. Follow that pattern for 15-30 minutes a day. Slowly make each run longer and each walk shorter. Later on, you can increase your distance, speed and exercise time.