15. It's already 10 o' clock. I wonder how it_________ that she was two hours late on
such a short trip.
.

6．Newly-developed materials for spaceships can___________extreme weather conditions.

 
34. For a long time she couldn’t ______ the fact of her son’s death.

29. High up in the mountains _____ a quiet small village, with only 20 households.

27. After his wife died, he kept himself _____ from other people and the outside world,

When a new disease breaks out，experts must     what to do in the fastest way．

Latest researches show children     with high levels of air pollution during their first
year of life run a greater risk of developing certain diseases．  

 
29. Tired of work through the year, she desired to _____ and make an independent life for     
herself.

 
24. He apologized for his mistake, saying that he ___________no offence.

Had you joined the chat room ten minutes ago，you would have known what we
                about then．