Why does the iron-carbon phase diagram go only to 6.7% carbon? O a. 6.7% is a value defined in ASTM standards O b. It is the recommended value for structural steel O c. In an iron-rich material such as steel, each carbon atom bonds with three iron atoms to form iron carbide (Fe3C), which has 6.7% carbon by weight of the alloy O d. There is no scientific reason behind this value, and it is an arbitrary value. What is a typical carbon percentage in structural steel? O a. 0.25% O b. 6.7% O c. 0.025% O d. 2.5% Define alloy steels. Explain why alloys are added to steel? O a. Elements other than Carbon are added to make alloy steel to keep the cost of manufacture low. O b. Alloy steels are produced by adding mineral fibers to normal steels to improve their strength. O c. Alloy steel is one that is specially produced to achieve superior durability using a high Carbon content of 6.7% or higher. O d. Alloy steels are produced by intentionally adding one or more elements other than Carbon to improve the properties and other characteristics of steel. How would you describe a structural steel section with the standard designation W 36 x 182? O A wide-flange beam cross-section that is nominally 36 inches deep and weighs 182 ponds per linear foot O An I-beam cross-section that is nominally 182 centimeters deep and weighs 36 pounds per linear foot O A hollow tube with a circular cross-section that has a nominal diameter of 36 inches and weighs 182 pounds per linear foot O A wide-flange beam cross-section that is nominally 36 centimeters deep and weighs 182 kilograms per linear meter