Nowadays signs prohibiting smoking a common sight in restaurants, tea houses and shopping malls.
I want to ________ a question to the chairman but in a moment I lost my nerve.
The problem ________ this material can be used in our factory has been solved.
The first thing ________ I did was to see if there were any products ________ might help me, but there only seemed to be powders ________ to kill snakes.
________ is very important in doing any scientific work.
All efforts of cloning an animal will be ________ if there is not enough diversity in the group to overcome illness.