Every possible means_____ been tried,and we find only______ this means can we do it well.
Have you ever seen any trees ________ leaves were black because of the polluted air?
The scientist won the Nobel Prize in Chemistry, ________ made him famous all over the world.
The result was not the same ________ the professor had expected, ________ was rather disappointing.
Was it through Mary, ________ was working at a high school, ________ you got to know Tom?
Nowadays people are more concerned about the environment ________ they live.