It is the prevention of disease_____ its successful treatment that has led to the rapid increase of the world’s population.

 With April 18’s railway speedup, highway and air transport will have to compete with __________ service for passengers. 

I wasn’t blaming anyone; I           said errors like this could be avoided.

--___do you clean the reading room? ---Every two or three days.

The clerks were at work so ____ that nobody realized it was already lunch time.