Multiple choice

'A tube within a tube' body plan is met within

  1. hydra

  2. plannaria

  3. ascaris

  4. fasciola

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The tube-within-a-tube body plan refers to organisms with a complete digestive tract having both mouth and anus. Ascaris (a nematode) exhibits this body plan, unlike hydra and planaria which have a single opening (sac-like body plan).