Comprehension \( \quad: \) Consider a function \( f: R \rightarrow R \) such that \( (f(x)+f(z))...

Comprehension \( \quad: \) Consider a function \( f: R \rightarrow R \) such that \( (f(x)+f(z))(f(y)+f(t))=f(x y-z t)+f(x t+y z) \) where \( x, y, z, t \in R \)
For the non-constant function, \( f: R \rightarrow R, f(x) \) is
(a) Even
(b) Odd
(c) Neither even nor odd
(d) None of these