Option 1 suggests that penguins have a chemical substance in their muscles that is toxic to polar bears, preventing them from being preyed upon. However, there is no evidence or scientific basis for this claim. It is unlikely that penguins have developed a toxic defense mechanism specifically targeting polar bears.

Option 2 states that penguins are gregarious and always move in groups, making it difficult for a polar bear to approach them. This is a valid point as the collective movement and behavior of penguins can make it challenging for a predator to single out an individual for hunting.

Option 3 is the correct answer. It states that polar bears and penguins never coexist under natural conditions. Polar bears inhabit the Arctic region, while penguins live in the Antarctic region. The geographic separation of these two species makes it unlikely for them to encounter each other in the wild.

Option 4 suggests that polar bears and penguins display symbiotic relationships and help each other for their existence in the ice-cold ecosystem. However, there is no evidence to support this claim. Polar bears and penguins have different habitats and ecological roles, and there is no known beneficial interaction between them.

In conclusion, the correct explanation for why polar bears do not prey on penguins is due to the