Winter in the north is usually very cold and it is important to avoid colder-related injuries such as frostbite(冻伤) and hypothermia(体温降低)．Frostbite is damage that happens when skin is exposed to extreme cold for too long．It mainly happens on the hands，feet，nose，and ears and some will bring permanent damage．Hypothermia is a serious medical condition caused by serious cold．It happens when the body cannot produce as much heat as it loses．If not treated，it can be deadly．
The best way to avoid cold-related injuries is to be prepared for the outdoors．Here is a simple way to remember four basic steps to staying warm．Think of COLD．
The C stands for cover．Wear a hat and scarf to keep heat from escaping through the head，neck，and ears．And wear mittens instead of gloves．Mittens are a type of glove that does not have separate parts for each finger．Gloves may not keep hands as warm because they separate the fingers．
The O stands for overexertion(过分用力)．Avoid activities that will make you sweaty．Wet clothes and cold weather are a bad mix．
L is for layers．Wearing loose，lightweight clothes，one layer on top of another, is better than single heavy layer clothing．Also，make sure outerwear is made of water resistant and tightly knit material．
The last letter D stands for dry．In other words，stay as dry as possible．Pay attention to the places where snow can enter, like the tops of boots．the necks of coats and the wrist areas of mittens．
And there are a couple of other things to keep in mind，one for children and the other for adults．Eating snow might be fun but it lowers the body's temperature．And drinking alcohol might make a person feel warm，but what it really does is weaken the body's ability to hold heat．
67．Both frostbite and hypothermia        ．
A．are injuries caused by extreme cold
B．may happen on the hands，feet，nose and ears
C．may cause uncontrollable shaking and slow breathing
D．may be deadly injuries
68．Mittens can keep your hands warmer than gloves because           ．
A．they are thicker                     B．they are made of better materials
C．they don't separate your fingers        D．they separate your fingers
69．      can help you avoid cold-related injuries．
A．Trying your best to exercise until you get sweat
B．Wearing layers of loose，lightweight clothes
C．Drinking alcohol to make you feel warm
D．Wearing a single heavy layer of clothing
70．Overexertion should be avoided because         ．
A．it may exhaust you       B．it may make you hungry
C．it may make you sweat     D．it may lower your body temperature