Final answer:
The correct answer is 'b) Sleeping, observation' which refers to types of passenger rail cars designed for overnight accommodation and scenic viewing, respectively.
Step-by-step explanation:
The question is related to rail transportation and the types of cars ordered and delivered for a rail service. The correct answer is b) Sleeping, observation cars. These terms pertain to the types of passenger rail cars. Sleeping cars are railway passenger cars that can accommodate passengers overnight with sleeping facilities.
On the other hand, observation cars are designed to allow passengers to view the scenery from large, scenic windows, usually at the end of a train, and often have features like a rounded or open-end platform. These terms are significant in railway transportation history and in understanding the different types of services and amenities offered by rail companies.