My 9-year-old son spends a lot of time on the computer surfing the Internet and sending instant messages to his friends. But I worry about him getting into trouble with strangers online.What can I do to protect him?

—Brian

Simple surfing and instant messaging with friends are common activities for kids—and generally safe, if you’ve discussed some rules of use with them. Chatting with strangers, however, may be a different story. Although there’s no way to know the actual risk,   the FBI (联邦调查局) warns that kids whose Internet activity isn’t monitored are most at the risk of being exploited (利用).

Keep the computer in a common room in the house rather than in your son’s bedroom. Take an interest in the sites your son is visiting and the people with whom he is chatting.Warn him never to give out his personal information (his phone number, name, address, school name, etc.), agree to meet in-person anyone he meets in a chat room,or share any photographs.

Urge your son to introduce you to any new “friends” he meets online and to tell you if he ever feels uncomfortable about conversations that take place. Most importantly, talk to him about the dangers of interacting with strangers online and remind him that people online often don’t tell the truth. The FBI also recommends that parents maintain access to young kids’ online accounts and often check their email.

Finally, you can use parental controls offered by your Internet service provider or through blocking and filtering (过滤) software.

AC/DC have postponed their US, tour after singer Brian Johnson was warned by doctors that he was at risk of“ total hearing loss". This is unsurprising that the Australian band has been pumping out the hard rock decibel(分贝). But deafness isn’t only a concern for rock musicians. Anyone around music a lot has reason to be equally worried.

When you are exposed to music, risk to hearing arises from a combination of how loud the sound is and how long you’ re exposed to it for. If you visit a nightclub with music at 100 dB, then after only 10~15 minutes the exposure is potentially damaging. In a quieter part of the club, but where the music is still loud enough that you have to shout at your friends, them you could be there for a couple of hours before having to worry about your hearing. Of course music frequently exceeds (超过) 80~85 dB, but what counts most in assessing the risk to hearing is the average exposure.

Exposure to high noise levels often causes temporary deafness-something many people have experienced after going to a nightclub. While hearing usually recovers , repeated loud exposure leads to permanent hearing damage. Initially, this damage is unlikely to be noticed by the listener. Problems only become significant in middle age when the noise-caused hearing loss combines with the natural loss of hearing due to ageing.

Often orchestras employ screens or “musicians ear plugs” to block sound from the loudest instruments. These decrease sound without completely blocking everything out and are very useful in rehearsal(训练), but get in the way of balancing the sound in a concert. Professional orchestras also look at how they schedule music to ensure that musicians are exposed to a mixture of quiet and loud pieces. Given how loud their instruments are, drummers are particularly at risk, but using era plugs can go some way to reducing potential hearing loss. For rock and pop musicians, using in-ear monitors has the potential to reduce noise exposure.

Improved technology means the number of musicians having to give up performing could decrease, But student musicians need to be educated about the dangers of noise-caused hearing loss. The increasing use of headphones will also work against this. Unless people are careful with the volume level on their portable music players, hearing loss caused by music will increase.

Your health is one of the most valuable things you have.【小题1】Using strategics to help develop your immune system and reduce habits that harm your immunity can help you live a healthier, happier life.

Exercise daily. Establishing a moderate exercise routine can help you be healthier overall. That increased health both boosts your natural immunities and can help you get over illness more quickly. Try going for a walk for at least 30 minutes most days. Find a walking buddy to keep you motivated and accountable.【小题2】. If you don’t like exercising, try getting involved in a sport or finding an active hobby that will “trick” you into exercising while you are having fun.

【小题3】. Many Americans have a vitamin D deficiency, which has long-ranging effects on human health. The best way to boost vitamin D levels is to have moderate exposure to direct sunlight. The fresh air won’t hurt either!

Sleep at least 7-8 hours each night.【小题4】Getting an adequate amount of sleep at night can help your body become refreshed and build its natural defenses. Additionally, getting extra sleep at the first sign of illness can help you bounce back more quickly.

Avoid cigarette smoke. You should certainly avoid smoking yourself for many health reasons, but even being around other people who are smoking can decrease your immune function. If you are a smoker, you should quit. If your friends or family members are smokers, try encouraging them to quit.【小题5】