A、If they stay in a snow-covered area. B、If they do not keep themselves warm. C、If they do not take enough equipment. D、If they

If you are lost in the mountain, stay calm in the face of darkness, loneliness, and the unknown. It will greatly increase your chances of survival. Many people think that preparing necessary equipment and knowing how to use it are very important, but actually eighty percent of mountain survival is your reaction to fear. Find a hiding place.
    Unnecessary labor will make you sweat and make you cold. Find a hiding place around you before trying to start your own construction. If you are in a snow-covered area, you may be able to dig a cave in deep snow for protection from the wind. You should try to hide yourself in the middle of the mountain if possible. Stay out of the valleys where cold air falls, and the valley floor can be the coldest area on the mountain. Signal rescuers for help.
    The best time to signal rescuers is during the day. Signal for help from the highest point possible — it will be easier for rescuers to see you, and any sound you make will travel farther. If you take a box of matches and a space blanket (a special blanket for traveling), build three smoky fires and put your blanket — gold side facing out — on the ground. Do not walk away.
    It will make finding you more difficult, as search teams will be trying to follow your path and may miss you if you have gone off in a different direction. Searchers often end up finding a car with no one in it.
    If you get frostbite (a condition caused by extreme cold, which makes your fingers and toes swell, become darker, and sometimes fall off), do not rewarm the affected area until you’re out of danger.
    You can walk on frostbitten feet, but once you warm the area and can feel the pain, you will not want to walk anywhere. Try to protect the frostbitten area and keep it dry until you are rescued.
Questions 30 to 32 are based on the passage you have just heard.
30. When lost in the mountains, what can one do to increase his chances of survival?
31. According to the passage, under what condition do people most probably fail to survive?
32. What can we infer from the passage?