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.

已知直线l∥平面α，l的一个方向向量为（t，2，4），α的法向量为（$\frac{1}{2}$，1，2），则实数t的值为____ 

七年级学生张宁同学向家人介绍的宋代城市风貌中哪个观点是错误（    ）