Final answer:
The main purpose of the passage 'Watch Out for the Octopus!' is to inform the reader about different poisonous and venomous animals, such as the puffer fish, poison dart frogs, taipan, scorpions, spiders, and the blue-ringed octopus.
Step-by-step explanation:
The main purpose of the passage titled Watch Out for the Octopus! is C. to inform the reader about different poisonous and venomous animals. This is evident from the detailed descriptions provided about various deadly animals, such as the puffer fish, poison dart frogs, venomous snakes like the taipan and king cobra, scorpions, spiders, and the octopus, emphasizing their dangerous characteristics and the effects they have on humans and other animals. While the passage also briefly touches on the reasons why certain animals are venomous or poisonous, and how some people interact with them, the primary focus remains on informing readers about these creatures and the potential dangers they pose.