3.He never leaves the lab until (before)11:00 in the evening.

He always stays in the lab till 11:00 p.m.

2.How long (Since when) have you been away from home?

How long have you not been (back) home?

How long is it since you left home?

1.This(The) new machine is made in China.

Before windows were used,old houses in Northern Europe and Britain were very dark.Their great rooms were high,with onlya (one) hole in the roof to let out the smoke (dust) from cooking fires.As time went on (by),people began to make the holes bigger so as to have more light and air in their homes.

The first English window was just a small opening in the wall.It was cut long,to let in as much light as possible ,and narrow,to keep out the bad weather.However,with the window cut long,more wind than light would come in.This is why it was called"the wind's eye ".And the word "window"　 comes from two ancient words for"wind" and "eye".

19.(D)tell　　　　　　　　　 20.(A)seeing the man before

17.(C)hasn't been painted　　 18.(B)up with

15.(C)is there　　　　　　　 16.(B)carries

13.(A)whether　　　　　　　　 14.(B)so that

11.(A)broke out　　　　　　　 12.(D)needn't come

9.(D)was raining　　　　　　 10.(D)besides