Which of the following is an advantage of a steam engine?

Choosing the option that states steam engines have a slow rotational speed without the need for reduction gearing reflects a true characteristic of these machines. Steam engines typically operate with a reciprocating motion, which naturally results in lower rotational speeds compared to many internal combustion engines. The design of steam engines often allows them to produce high torque at low speeds, making them suitable for applications where high initial torque is necessary, such as in locomotives or heavy machinery.

The ability to operate effectively at lower speeds without additional gearing simplifies the design and can reduce costs and mechanical complexity in certain applications. This efficiency at low speeds is particularly advantageous in situations where precise control and high torque are preferred.

While the other options may mention positive attributes relating to steam engines, they don't hold as strongly in this context. For instance, steam engines are not necessarily compact and lightweight, especially when compared to modern engines. They also typically do not rely solely on renewable sources, as they historically have used fossil fuels like coal. Lastly, while steam engines can require less frequent maintenance against certain specific types of engines, they can demand rigorous maintenance routines, especially in terms of boiler health and system integrity.