[练习题]Directions: Fill in the blank in each of the following statements with one word, the first letter of which is already given as a clue. Note that you are to fill in ONE word only, and you are not allowed to change the letter given.A r is often seen as part of a word; it can never stand by itself although it bears clear, definite meaning; it must be combined with another similar form or an affix to form a word.