Step 1: Know the matching tools. To match these animals we look at three features: number of germ layers (diploblastic or triploblastic), type of symmetry (radial or bilateral), and the body cavity or coelom.
Step 2: Place Hydra. Hydra is a cnidarian. It has only two germ layers, so it is diploblastic, and its body shows radial symmetry. This matches feature III.
Step 3: Place Ascaris. Ascaris is a roundworm. It has a body cavity that is not fully lined by mesoderm, called a pseudocoelom. So Ascaris is pseudocoelomate, which is feature I.
Step 4: Place Pheretima. Pheretima is the earthworm. It has a true coelom fully lined by mesoderm, so it is eucoelomate. This is feature II.
Step 5: Place Planaria. Planaria is a flatworm. It has three germ layers but no body cavity at all, so it is a triploblastic acoelomate. This is feature IV.
Step 6: Read off the final match. Putting it together gives A-III, B-I, C-II, D-IV, which is the second option. \[ \boxed{\text{A-III, B-I, C-II, D-IV}} \]
