Option (b) is correct.

A. "All fishes are mammals."

C. "No fishes are mammals."

These two propositions are contrary to each other because if proposition A is true, then proposition C must be false, and vice versa. If all fishes are mammals (A is true), then it contradicts the statement that no fishes are mammals (C). Likewise, if no fishes are mammals (C is true), it contradicts the statement that all fishes are mammals (A).

Propositions B and D are not contrary to each other because they can both be true at the same time. Proposition B states that "some fishes are mammals," which allows for the possibility of there being both fishes that are mammals and fishes that are not mammals. Proposition D states that "some fishes are not mammals," which aligns with the possibility mentioned in proposition B.

Therefore, the correct answer is (b) A and C Only.

विकल्प (b) सही है।

‘A’ प्रकार के वाक्य एवं ‘E’ प्रकार के वाक्य आपस में विपरीत होते है।

‘A’ प्रकार का वाक्य – “सभी मछलिया स्तनपायी होती है”, सार्वभौमिक सत्य है।

‘E’ प्रकार का वाक्य “कोई भी मछलियाँ स्तनपायी नही है”, सार्वभौमिक असत्य है।