Classification is a useful ______ to the organization of knowledge in any field.

With its moving story and the wonderful acting, the ______ film put on this week has attracted millions of audience and is well on the way to becoming the year’s top-grossing movie.

The old woman felt disappointed for she got nothing in _____ for her kindness. 

Now that taking exercise will build up your       , you should try to run in the morning.

The financial crisis has put the world economy in a difficult _________.