Which description fits the fuel tanks used in the boat?

The correct answer focuses on the specific characteristics of the fuel tanks used in the boat, noting that they hold 210 liters and are self-equalizing with two custom-sized metal tanks. This description is comprehensive because it provides detailed specifications about the tank's capacity and design.

The mention of being "self-equalizing" indicates that the tanks are designed to maintain a balanced pressure, which is crucial for preventing fuel spillage and ensuring safe operation. Additionally, the aspect of having "custom sized metal tanks" suggests that they are tailored specifically for the boat's design and requirements, which can enhance the efficiency and safety of the fuel system.

While other options may describe aspects such as being self-venting or part of a long service fuel system, they do not provide the same level of detail regarding the tank configuration and material that is essential for understanding how these tanks function within the larger system of the boat. This specificity about the fuel tank's construction and functionality makes this choice the most accurate representation.