设$\alpha$是第二象限角，$P\left(x,4\right)$为其终边上的一点，且$\cos \alpha =\frac{1}{5}x$，则$\tan \alpha =$(   )

引起传染病的细菌、病毒和寄生虫等生物，称为病原体，而能够散播病原体的人和动物叫____ ．计划免疫是预防传染病的一种简便易行的手段，这一手段是属于防治传染病措施中的____ 。

Dear Abby，

    I'm a helpless mother. My son Tom is 15 years old. I find that the older he grows， the less we talk. I feel very sad and I really need help.

    My first problem is about his hobbies. He spends almost all his spare time on computer games. When he gets home， he always turns on the computer and closes the door. I'm getting worried about him， especially when his English teacher tells me he always gets low marks in the English exams.

    Second， he likes new technology， but I don't have enough money and I can't afford all the things he wants.

    Recently， I've found that he is always alone. I've never seen him talking to his friends on the phone or going out with anyone on weekends. That is the last problem I have.

    What should I do to help him? Please give me some advice.

A helpless mother

宽容是中华民族的传统美德，下列与之相印证的是（  ）

①山锐则不高，水狭则不深            ②毋以小嫌疏至亲，毋以新怨忘旧恩 

③以大度兼容，则万物兼济            ④自喜蜗牛舍，兼容燕子巢