题目

阅读短文，根据其内容，完成下列任务。 If you fall off a bike and break your arms,it happens very quickly. But computer injuries happen slowly. You probably know how to ride a bikesafely. Now let's learn to ①acomputer safely. Youreyes. Too much light can injure your eyes. Your eyes should be more than50cm from the screen. Don't forget to look away from it sometimes. This givesyour eyes a rest. Yourhands and wrists (手腕). Hand and wrist injures can happen because the hands and wristsare moved in the same way hundreds of times. If you use keyboard for a longtime, follow theNa2S2O5是常用的防腐剂和漂白剂。可利用烟道气中的SO2生产Na2S2O5，其流程如下：下列说法正确的是A. 上述制备过程所涉及的物质中只有一种酸性氧化物B. Na2S2O5作防腐剂和SO2作漂白剂时，均表现还原性C. 上述流程中的Na2CO3饱和溶液和Na2CO3固体不可互换D. 实验室模拟“结晶脱水”时用到的仪器只有蒸发皿、玻璃棒、烧杯、漏斗