接种疫苗是预防传染病的一种最简便、最经济最易行的手段．（判断对错）

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    Recently，there was a report about a special app called "notOK"．A 13-year-old girl Hannah Lucas and her brother Charlie put their heads together to create this app last year．

    Hannah has been suffering from an illness that causes her to pass out since she was little．This is very dangerous if there is no one around．She was also being bullied(欺凌)by some students at school．So she searched for an app that would allow her to press a button so that a friend or a family member would know immediately that she needed help．After realizing there was no such thing，Hannah and her brother decided to do something about it．After some research，Hannah made some early drawings of what the app might look like．Then，after taking a programming class，Charlie began to think about the best way for the app to work．

    They wanted something that would send a text message to up to five contacts that reads："Hey，I'm not OK．Please call me，text me，or come and find me"，along with a link to the user's current GPS location．

    They started looking for someone to help them make the app．And when Hannah shared her dream with people in a summer business class which she attended two years ago，they were really excited about the app．They thought of many different marketing ideas．By mid—December last year, "notOK" app was finished as a birthday present for Hannah from Charlie．"It was exactly what we wanted，"Charlie said．

    In today's age，most people will agree that apps like these are great．Whether you're suffering from illness，or anything emergent(紧急的)，writing a text message or making a phone call to get the help you need can be difficult．

    Hannah is happy to know that her app will help more people．"It's like I went through my dark times so I could help people through theirs，"she said．

阅读理解

    Sunscreens (防晒霜) can offer protection from two types of ultraviolet (UV) rays (紫外线): UVB, which according to the Skin Cancer Foundation, are the chief cause of sunburn and play a key role in the development of skin cancer, and UVA, which get through the skin more deeply and are largely responsible for skin aging and wrinkling, as well as skin cancer risk. The SPF (防晒指数) measurement on sunscreens refers to the UVB protection level — and the number may not mean what you think it does. SPF 15 doesn't protect you from 15% of UVB rays, just as SPF 100 doesn't protect you from 100% of the rays. In fact, as you get into the higher numbered SPF sunscreens (think: 50 and above), the difference in UVB protection is actually pretty small.

    Theoretically, though the increase in UVB protection with a super-high SPF sunscreen may be not worth considering, it may help, and certainly can't hurt, to use it — that is, as long as you do so correctly. “The only downside is whether you're giving yourself a sense of false security,” Dr. Gohara says.

    Indeed, as Dr. Wang also pointed out, when people choose increased SPFs, they may actually feel so protected by the product that they finally ignore proper sun protection. “When people use really high SPF products, they tend not to reuse, they tend to stay out in the sun much longer, and they don't use other protective measures such as clothing and hats,” he says. Regardless of any increase in protection that a high SPF may or may not offer, one thing is certain: It doesn't give your body a free pass from sunburns, aging, or cancers, and it doesn't protect you from those things for any greater length of time than the lower SPF options. Both Dr. Wang and Dr. Gohara emphasized that, no matter what the SPF is, it's important to reapply your sunscreen every two hours.