Which material is the softest and most easily punctured for cargo tanks?

The correct answer is aluminum because of its physical properties that make it softer and more malleable than steel or iron. Aluminum has a lower tensile strength compared to these metals, which means it can be more easily deformed and punctured under pressure or impact. This characteristic is a crucial consideration in the design and construction of cargo tanks, particularly when dealing with hazardous materials where the integrity of the tank is paramount for safety.

When discussing the options, steel and iron are both much stronger and more rigid, making them less susceptible to puncturing than aluminum. Plastic, while it can be lightweight and resistant to corrosion, generally does not provide the same structural integrity required for transporting hazardous materials in cargo tanks. It is usually used in specific applications where flexibility and lower weight are prioritized over strength, but it may not hold up as well under the stress that cargo tanks typically encounter.

Overall, when evaluating materials for cargo tank construction, aluminum's softness and ease of puncture become significant factors in contexts where lighter weight is beneficial, but safety and material properties must always be considered.