Decide, in which of the cases it is true that 
the type of variable s a type parameter?

a) class R implements Comparable<String> {
         String myComparable = "Hello World";
         public int compareTo (String str) {
             return this.compareTo(str);
         }
   }
   R s;
b) class B {}
   class A<T extends B> {
      T s;
      T getS() {
        return s;
      }
   }
c) Object s = new String(“This is a string”);
d) class T {}
   class S extends T {}
                
   T s = new S();