A learner makes a note: an octopus captures prey with flexible arms and shows complex behaviour. The missing scientific idea is:

Correct Answer: D

well-developed head and arms

Cephalopods have a well-developed head, arms or tentacles, advanced eyes, and a complex nervous system. They are the most active molluscs. This MCQ belongs to the Cephalopoda topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.