Step 1: Understanding the Concept:
This question requires geographical knowledge of the route of the Trans-Siberian Railway, one of the longest railway lines in the world, which crosses Russia from its capital in the west to the Pacific coast in the east.
Step 2: Detailed Explanation:
The Trans-Siberian Railway's main route runs from west to east. Let's place the given cities in that order:
(A) Moscow: Located in European Russia, it is the western terminus of the railway.
(B) Kazan: A major city on the Volga River, located to the east of Moscow.
(C) Omsk: A large city in southwestern Siberia, situated further east than Kazan, on the Irtysh River.
(D) Chita: Located in eastern Siberia, significantly further east than Omsk, and is a major junction on the railway.
The correct geographical sequence from west to east is Moscow $\rightarrow$ Kazan $\rightarrow$ Omsk $\rightarrow$ Chita.
Step 3: Final Answer:
The correct order is (A), (B), (C), (D).