Option (c) is correct.

because the statements "All Biologists are outstanding teachers" and "No Biologists are outstanding teachers" cannot both be true at the same time, but they could both be false.

If we assume that "All Biologists are outstanding teachers" is true, then "No Biologists are outstanding teachers" must be false. However, it is possible that some biologists are outstanding teachers and some are not, which means that both statements could be false.

Similarly, if we assume that "No Biologists are outstanding teachers" is true, then "All Biologists are outstanding teachers" must be false. However, it is also possible that some biologists are outstanding teachers and some are not, which means that both statements could be false.

विकल्प (c) सही है।

विरोध के परंपरागत वर्ग (classical square of opposition) के अनुसार, A और E वे कथन हैं जो एक साथ सत्य नहीं हो सकते परन्तु असत्य हो सकतें हैं। इस आधार पर, दिए गए विकल्पों में, "सभी जीवविज्ञानी उत्कृष्ट शिक्षक होते हैं" [A प्रकार] और "कोई भी जीवविज्ञानी उत्कृष्ट शिक्षक नहीं होता है" [E प्रकार] ही वे कथन हैं।