p
q
r
s
Correct answer is B
The identity element (e) under an operation, say \(\otimes\), is the element such that for any given element under the operation, say a,
\(a \otimes e = e \otimes a = a\)
From the table, q is the identity element.
\(p \otimes q = q \otimes p = p\)
Same as all through.