Remember key larval forms and their associated phyla. Trochophore for Annelids/Molluscs, Bipinnaria for Echinoderms, Planula for Cnidarians, and Miracidium for Platyhelminthes (flukes).
Step 1: Match each larval form with its respective Phylum.
\begin{itemize}
\item A. Trochophore: The trochophore larva is a characteristic free-swimming larval stage found in many marine invertebrates, particularly in Annelida (segmented worms) and Mollusca.
\item Therefore, A matches with II. Annelida.
\item B. Bipinnaria: The bipinnaria larva is a characteristic free-swimming larval stage unique to certain members of the phylum Echinodermata, specifically starfish (Asteroidea).
\item Therefore, B matches with IV. Echinodermata.
\item C. Planula: The planula larva is a free-swimming, ciliated, and elongated larval form found in most species of the phylum Cnidaria (e.g., jellyfish, corals, sea anemones). It settles down to form a polyp.
\item Therefore, C matches with I. Cnidaria.
\item D. Miracidium: The miracidium larva is the first larval stage of digenetic trematodes (flukes), which are parasitic flatworms belonging to the phylum Platyhelminthes. This larva is typically free-swimming and infects a snail intermediate host.
\item Therefore, D matches with III. Platyhelminthes.
\end{itemize}
Step 2: Combine the matches.
A - II
B - IV
C - I
D - III Step 3: Check against the given options.
\begin{itemize}
\item Option (1) A-II, B-V, C-III, D-IV (Incorrect, B and D are wrong)
\item Option (2) A-IV, B-II, C-III, D-I (Incorrect, A, B, and D are wrong)
\item Option (3) A-III, B-V, C-IV, D-II (Incorrect, A, B, C, and D are wrong)
\item Option (4) A-II, B-IV, C-I, D-III (Matches our derived combinations)
\end{itemize}
The final answer is $\boxed{\text{A-II, B-IV, C-I, D-III}}$.
