Which of the following sets of organisms represents the correct trends from simple to complex structural organization? 1. Mollusca 2. Platyhelminthes 3. Nematoda 4. Protozoa

• A.4 → 1 → 2 → 3
• B.4 → 3 → 2 → 1
• C.4 → 2 → 1 → 3
• D.4 → 2 → 3 → 1
• E.