In the environment area, there is a system ________ the waste is disposed of by using the principles of ecology.
I found the door __________ when I got home.
I can make you __________ what I say, but you can't make yourself __________ in English.
The doctor asked him not to leave his wound __________.
The TV play was so fascinating that the children kept their eyes __________ on the screen.
With nothing __________ to burn, the fire became weak and finally died out.