The 1986 Challenger space-shuttle （）was caused by unusually low temperatures immediately before the launch.

Others viewed the findings with （）noting that a cause-a...

单项选择题Others viewed the findings with （）noting that a cause-and-effect relationship between passive smoking and cancer remains to be shown.

In those days, executives expected to spend most of the...

单项选择题In those days, executives expected to spend most of their lives in the same firm and, unless they were dismissed for （）to retire at the age of 65.

He was looking admiringly at the photograph published b...

单项选择题He was looking admiringly at the photograph published by Collins in （）with the Imperial Museum.