It was a very 小题1:_____(fog) day in London. The fog was so thick 小题2:____ it was impossible to see 小题3:_____(many) than a foot or so.Buses, cars and taxis were not able to run and were standing by the side of the road.People were trying to find their way about on foot but were losing their way in the fog.

Mr. Smith had a very important meeting at the House of Commons and had to get there but no one could take him.

　 He tried to walk there 小题4:____ found he was quite lost. Suddenly he bumped into a stranger. The stranger asked小题5:____he could help him. Mr. Smith said he wanted to get to the Houses of Parliament. The stranger told him he would take him there.Mr. Smith thanked him and they started to walk there. The fog was getting thicker every minute but the stranger had no difficulty in小题6:_____(find) the way.

　　He went along one street, 小题7:______(turn) down another, crossed a square and at last after about half小题8:_____hour's walk they arrived at the Houses of Parliament.　Mr. Smith couldn't understand how the stranger found his way. "It is wonderful,” 小题9:____ said. "How do you find the way小题10:____this fog?" "It is no trouble at all to me," said the stranger, "I am blind."

热水锅炉产生汽化现象时，（）。

A.锅内有水击响声

B.炉膛温度升高

C.燃煤量增加

D.给水量增加