d
(d)Arsenic has five valence electrons, so it a donor impurity. Hence \(X\) becomes \(N-\)type semiconductor. Indium has only three outer electrons, so it is an acceptor impurity. Hence \(Y\) becomes \(P-\) type semiconductor. Also \(N\) \((i.e.\, X)\) is connected to positive terminal of battery and \(P(i.e\, Y)\) is connected to negative terminal of battery so \(PN-\) junction is reverse biased.