Nowadays, you can see many people busy on their smartphones(智能手机) if you look a____. Smartphones make our lives easier. But have you ever thought a____ what they mean to your eyes? Staring(盯) at smartphones for long time gives you dry eyes and even causes a disease ____ (叫做) glaucoma(青光眼).   

    While you're probably not going to stop using your smartphone, there are a few things you can do to protect your eyes. Hold your phone at least 30 cm away from your eyes when using it. Take a break every ____ (小时) and try the following: look at something at least five meters away from you and then focus on the tip of your nose. Repeat this s____ times. It should reduce(减少) the discomfort in your eyes.

正在生长发育时期的青少年，应多吃下列哪一组食物

我国是一个以外流河为主的国家，下列关于我国外流河和内流河的分布，叙述正确的是（    ）