.________ gas leaks and similar accidents should occur, some responsible persons should regularly inspect all the laboratories.
Two lawyers have donated $50,000 to ________ our school’s campaign “Help the Needy”, which was started by our former headmaster three years ago.
The new safety regulations were agreed on after _____ with the work-force.
Our goods with a (an) ________of colors and patterns can meet the demand of customers at different levels.
If you want to see the chairman of the department, you’d better make an _________ with his secretary first.
It was along the Mississippi River _________ Mark Twain spent much of his childhood.