All through the winter，the Esquimaux（爱斯基摩人） live in houses made of snow．These small houses are very clean and white when they are new．They can soon turn dirty，but pieces of fresh snow make them new again．

Sometimes the Esquimaux build their small houses with the wood that they find along the seaside．However，they aren't always so lucky．When they can't get wood，they use the snow．It is so cold that the snow becomes very hard，so the small houses are strong enough in the whole winter．The windows of these houses are not made of glass，but of ice．

When the warm weather comes，the houses become water slowly．The Esquimaux get wet as they lie in bed，and often catch a cold．They are glad to get away from the small snow houses and live in their tens during the summer．

49．The Esquimaux live in houses made of 　　all through the winter．

A．	glass
B．	snow
C．	paper
D．	grass

50．Sometimes the Esquimaux build their small houses with the wood that they find 　　．

A．	in the river
B．	in the snow
C．	along the seaside
D．	in the mountains

51．The Esquimaux live in their tents when 　　．

A．	the snow houses are dirty
B．	it is summer
C．	they get some wood
D．	it is spring．