5. Why the explosion occurred was ________ the laboratory attendant had been careless．

2. —How was the journey? Did you come back by plane or by train?—For some reason. I came back by train. I _____ back by plane, though.

50.Journalists have to be very independently, and they need many different skill. 

9.（ ）是掌握操作技能的开端，需要以认知为基础。

44.I ______ not being able to return their invitation.

48.The 42% of Americans who have at least one step-relative typically feel a stronger sense of obligation to their biological parent, child or sibling than to their step-relatives.

三、判断题（10分。正确请选择A，错误请选择B。）46. The study was published in latest issue of the journal Pediatrics.

47.Scarcely had we arrived at the farm when we spotted many oranges hang from the branches. 

11.It was at eleven o’clock _____ they went out of the cinema.

38.The film we saw last night was ______ good.

55.After we paid the oranges we harvested, we headed back home. 

21.—Will you have a second child?—Haven’t decided yet. We ________ about it the whole year.