Step 1: Identify the defining feature of each toy set:
\begin{itemize}
\item P: Inflatable animal toy — soft, air-filled, rounded form.
\item Q: Nesting dolls — objects of similar shape and size that fit into one another.
\item R: Building blocks — modular, stackable components.
\item S: Spinning top — rotational symmetry and balance.
\end{itemize}
\bigskip
Step 2: Identify the corresponding furniture characteristics:
\begin{itemize}
\item I: Modular sofa pieces — rearrangeable and block-like.
\item II: Spinning stool/table — rotational symmetry.
\item III: Inflatable seating — soft, air-filled shapes.
\item IV: Child furniture set — modular, block-assembled structure.
\end{itemize}
\bigskip
Step 3: Match based on shared functional or structural features:
\begin{itemize}
\item P $\rightarrow$ III (inflatable forms),
\item Q $\rightarrow$ I (nested / layered structure),
\item R $\rightarrow$ IV (block-based modularity),
\item S $\rightarrow$ II (rotational symmetry).
\end{itemize}
\bigskip
Final Answer:
\[
\boxed{D}
\]
\bigskip