UGC NET Paper 1 GA 2017 Jan Solved Paper

Among the following propositions two are related in such a way that they cannot both be true but can both be false.
Select the code that states those two propositions.
Propositions:
(A) Every student is attentive.
(B) Some students are attentive.
(C) Students are never attentive.
(D) Some students are not attentive.