The syntax of If-then-else in prolog goes the following way
(A $\rightarrow$ B ; C ) :
call(A),
!,
call(B)
(A $\rightarrow$ B ; C ) :
call(C)
So according to the above syntax, the correct answer will be
(B) if-else (G, P, $\Theta$) :- call(G), !, call(P). if-else (G, P, $\Theta$) :- call($\Theta$).