Which sentence uses a hyphen correctly? a. i have to buy my grand-father a present. b. i need thirty-six colors for this painting. c. i looked under the bed-and there it was! d. i've only read one-third-of the book so far.

Use of Hyphen(-)
Hyphens are used divide words at the end of line when the word cannot fit on the remainder of the line. There are six rules to follow.

1. Divide the word between syllables. It means, that one-syllable words are NEVER divided. 
      
     Incorrect    Incorrect    Correct       

     sp-             su-             sup-
     orts            pport          port

2. The hyphen goes at the end of the firts line.

         Incorrect    Correct
      
        sup-            sup-
        -port            port

3. Prefixes and suffixes make natural divisions.

     Incorrect     Correct

     in-               inter-
     ternational  national

4. Do not divide proper nouns or adjectives.

  Incorrect     Correct

  Pakis-         Pakistan
  tan

5. There should be at least two letters plus the hyphen on the first line and three letters on the second line.

   Incorrect         Incorrect         Correct  

   s-                    supposed-       sup-
   upposedly      ly                      posedly

6. Divide hyphenated word using the hyphen already in the word.

   Incorrect     Correct 

   moth-          mother-   
   er-in-law     in-law