yesterday ,the professor gave us a lecture __________the living animal.
what had happened ________ him?
_______ fact, he is right.
natural rubber is used ________ large amounts.
the man who is working ______ the desk is our teacher of english.~
we must do everything we can to build our country _________ a powerful and modern one.!!
more and more programs are televised _________ all over the world...
i use a pen ________ writing letters...
the earth travels ________ the sun ______ a fixed path...