A programmer is reading some documentation about the Character class 
in the Java library. The documentation contains the following example
of client code:

   if (Character.isLetter(c))
   {  ...
   }

From this, which of the following does s/he correctly conclude?
 (a) isLetter is an instance variable
 (b) isLetter is an instance method
 (c) isLetter is a class variable
 (d) isLetter is a class method
Select the most appropriate answer.