Which of the following statements are so related that they can neither both be true nor can they be false together?
A. No saints are materialists.
B. All saints are materialists.
C. Some saints are not materialists.
D. Some saints are materialists.
Choose the correct answer from the options given below:

Correct option is C

Statements A and D are contradictory statements, which means that they cannot both be true and they cannot both be false. If statement A is true, then statement D must be false, and vice versa. For example, if the statement "No saints are materialists" is true, then the statement "Some saints are materialists" must be false.
Statements B and C are contrary statements, which means that they cannot both be true, but they can both be false. For example, if the statement "All saints are materialists" is false, then the statement "Some saints are not materialists" may also be false.
Therefore, the only pair of statements that cannot both be true nor can they be false together is A and D.