Concept:
The Trans-Canadian Railway is a massive transcontinental link. Understanding its route involves knowing the sequence of major provinces and their central cities across Canada from the Atlantic side to the Rocky Mountains.
Step 1: Mapping the stations from East to West.
• D. Montreal: Located in Quebec in Eastern Canada. It is one of the easternmost major hubs of the railway.
• A. Winnipeg: Located in Manitoba. It is often called the "Gateway to the West" as it sits at the transition from the eastern forests to the western prairies.
• B. Regina: Located in Saskatchewan. It is west of Winnipeg in the heart of the Canadian Prairies.
• C. Calgary: Located in Alberta. It is the furthest west among these options, situated at the foothills of the Canadian Rockies.
Step 2: Establishing the sequence.
The correct order following the rail line toward the Pacific is: Montreal (D) $\rightarrow$ Winnipeg (A) $\rightarrow$ Regina (B) $\rightarrow$ Calgary (C).
Step 3: Conclusion.
The sequence matches option (1): D, A, B, C.