Mark the correct alternative in each of the following:
Q+ denote the set of all positive rational numbers. If the binary operation  on Q+ is defined as a
 on Q+ is defined as a  , then the inverse of 3 is
, then the inverse of 3 is
For Identity element a * e = a = e * a, with ‘e’ being the identity element.
Given 
⇒ 
⇒ 
For Inverse element a * b = e = b * a , with ‘b’ being the inverse element ‘a’.
Given 
Now for a = 3
⇒  ….(1)
 ….(1)
⇒  ….(2)
 ….(2)
⇒  is the required inverse element of a=3.
 is the required inverse element of a=3.