—How did you sleep last night?  —Like a log. Never slept ____. 

The great contributions he made______our country is_______worth remembering.

It is most _____that the environmentalists will come to the area to investigate the possible damage caused by the serious pollution.

 As a scientist, Madam Curie devoted herself ________ to her research and that was why she was given two Nobel Prizes.

The problem is _____ difficult for me _____ solve.