In a specimen-based viva, the examiner describes this case: a worm-like animal moves actively in one direction and has a clear anterior end. Choose the concept that fits it best.

Bilateral symmetry is associated with active directional movement and cephalization. It produces right and left halves and often allows development of a head region containing sensory structures. This MCQ belongs to the Animal architecture topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.