What is true about cast iron?

Cast iron is indeed strong when compressed, making it suitable for various construction and engineering applications. This characteristic arises from its high compressive strength, which allows it to withstand significant loads without deformation or failure. In practice, cast iron is often used for products like pipes and machinery bases where it will primarily bear loads in compression rather than tension.

The other properties listed in the question do not accurately describe cast iron. Unlike materials that are malleable or ductile, cast iron is generally brittle, which means it cannot be easily bent or forged. Its tensile strength is relatively lower compared to other metals, meaning it does not perform well under tensile stresses. These properties combined give cast iron its unique strengths and weaknesses, ultimately influencing its applications in design and manufacture.