Step 1: Understanding the animal and its residence.
- \textit{Ascaris lumbricoides} is a roundworm that resides in the small intestine of humans.
- \textit{Dracunculus medinensis} is the guinea worm, which resides in the subcutaneous tissue of humans.
- \textit{Enterobius vermicularis} is the pinworm that resides in the caecum or vermiform appendix.
- \textit{Wuchereria bancrofti} is a parasitic worm that resides in the lymphatic vessels and lymph nodes.
Step 2: Analyzing the options.
- (A) Incorrect, as it mismatches the habitat of \textit{Enterobius vermicularis}.
- (B) Incorrect, as \textit{Dracunculus medinensis} should reside in the subcutaneous tissue, not in the caecum.
- (C) Incorrect, \textit{Wuchereria bancrofti} should reside in the lymphatic vessels, not the subcutaneous tissue.
- (D) Correct, it correctly matches each organism to its respective tissue or organ of residence:
\textit{Ascaris lumbricoides} in the small intestine, \textit{Dracunculus medinensis} in the subcutaneous tissue, \textit{Enterobius vermicularis} in the caecum or vermiform appendix, and \textit{Wuchereria bancrofti} in the lymphatic vessels and lymph nodes.
Step 3: Conclusion.
The correct answer is (D) P-(iii), Q-(i), R-(iv), S-(ii).