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).