He made another wonderful discovery, _____ of importance to science.
It can take up three months to _____ a man to do this work.
The man who makes no mistakes usually makes _____.
It was not easy for him to buy good shoes because he had such a big _____ of feet.
We had a long meeting yesterday. It _____ four hours.
--- Mr. Lee wishes to see you. --- _____ him in.