Step 1: Recall key functions.
Cerebellum \(\Rightarrow\) coordination/fine motor control \(\Rightarrow\) (iii).
Thalamus \(\Rightarrow\) sensory relay to cortex \(\Rightarrow\) (iv).
Tectum (superior/inferior colliculi) \(\Rightarrow\) orienting reflexes to sights/sounds \(\Rightarrow\) (i).
Medulla \(\Rightarrow\) autonomic control of heart rate, circulation, respiration \(\Rightarrow\) (ii).
Step 2: Map and choose.
Thus \(P\!\to\!(iii),~Q\!\to\!(iv),~R\!\to\!(i),~S\!\to\!(ii)\), which matches option (D).
Final Answer: (D)