No one has yet succeeded in explaining the ___ of how life began.

Nobody knows how he was murdered, but _______ people behind the scenes can guess why. 

Hardly a month goes by without ______ of another survey revealing new depths of scientific illiteracy among US citizens.

Used to TV shows, where everything is quick and entertaining, many people do not have the _______ to read a book that requires thinking.

I caught a _____ of the car before it disappeared around the bend.