第三部分阅读理解（共20小题；每小题2分，满分40分）
Housing is always an important comcern,and things were no different back in Canada`s early days.The nailve population had several answers to the housing problem．
The igloo if a house built of ice or snow and is still in use today in more primitive areas of Canada`s north．The Inuit people find them the best type of housing,eSpecially when away from home on hunting or fishing trips.The igloos used o such trips are smaller and only temporary homes to be used for a few nights at most．Igloos are domeshaped（圆顶形的）and made of blocks of ice or snow.First a hole is dug out in the snow and this forms the lower part of the igloo.Then the blocks of ice or snow are built in a slope inwards and upwards from this base.Often a short tunnel leads to the door.This prevents the cold winds and snow blowing into the structure.
Tipis（or tepees）are the conical（圆锥形的）tents used by the majority of native People
across America.Some Canadian aboriginal people still prefer them to other types of housing. These structures are formed by a frame of poles covered with，usually，iether buffalo hide（水牛皮）or birch bark（桦树皮）．A hole at the top lets out the smoke from the cooking fires．Native people mostly travel from place to place,following their food supple across the countryside.Tepees are easy to taKe down，carry and put up at the next stopping place．
Another type of house iS the long house.This is exactly what the name suggests-a long narrow building that could house ten to twenty families.Built of poles covered with hides,there houses are common to the Iroquois people of 0ntario and NeW York.These structures are also on the West Coast by the Squeamish Indians.They are usually occupied by an exended family and divided into individual rooms,each with its own cooking fire.They are decorated with totem emblems （图腾标志）and a totem pole by the front door tells the history of the family．
56.Which of the following pictures matches with the igloo?
57．The short tunnel leading to the door of an igloo is used to__________．
A.catch the animals B.decorate the igloo
C.fasten the igloo D.keep the gloo warm
58．Which of the following about a tiPi is NOT true？
A.It has a hole at the top.
B.It is made of poles covered with hides．
C.lt can be easily carried everywhere.
D.It has a firm base made of ice.
59. The underhned word "They" in the last paragraph refers to "________"．
A.Squeamish Indians B.Long houses
C.Families D.Individual rooms
6o. Where can we most probably read this passage?
A.In a medical journal. B.In a science report．
C.In a culture magazine．D.In a biology textbook．
五氧化二磷
；红磷量不足，装置漏气、未冷却到室温就打开止水夹等；