Concept:
Urban settlements are classified according to their population size.
Step 1: Recall the population hierarchy.
• Mega cities -- Population above 10 million.
• Metropolitan cities -- Population above 1 million.
• Class I cities -- Population above 100,000.
• Towns -- Smaller urban settlements.
Step 2: Arrange from highest to lowest population.
\[
\boxed{\text{Mega cities} \rightarrow \text{Metropolitan cities} \rightarrow \text{Class I cities} \rightarrow \text{Towns}}
\]
This corresponds to
\[
\boxed{(ii)\rightarrow(i)\rightarrow(iii)\rightarrow(iv).}
\]
Step 3: Final conclusion.
Hence, the correct answer is
\[
\boxed{\text{(C) }(ii),\ (i),\ (iii),\ (iv).}
\]