What is the role of carbon in steel?

The correct option is To increase its strength. This answer is correct because it matches the approved learning objective to recall that steels are alloys of iron containing carbon and sometimes other metals. (Chemistry only) in the subtopic Alloys as useful materials.

The correct option is To increase its strength. To increase its strength is correct because it directly supports the approved learning objective to recall that steels are alloys of iron containing carbon and sometimes other metals. (Chemistry only). This belongs to the subtopic Alloys as useful materials within Using materials, so the explanation must stay tied to that curriculum context. The other options are incorrect because they either do not answer this learning objective, use a vague statement, or move away from Alloys as useful materials.