Final answer:
Titanium is the reactive metal with a high melting point used in aerospace applications, chosen for its strength and low density. Its production is costly due to the difficulty in extracting it from ores and the fact that magnesium is the limiting reactant during extraction.
Step-by-step explanation:
The metal that matches the description of being a reactive metal with a high melting point, used in manufacturing rocket nose cones due to its low density and remarkable strength, is Titanium (b). Titanium is lighter than steel, highly resistant to corrosion, can withstand extreme temperatures, and as a result, finds wide application in the aerospace industry and in medical implants as well as portable computer housings. Its production involves a key step where titanium tetrachloride (TiC) is converted to metallic titanium using molten magnesium metal at high temperatures, where magnesium serves as the limiting reactant in the process. Although titanium has many desirable properties such as being 45% lighter than steel and twice as strong as aluminum, it is difficult to extract from its ores, which contributes to its high cost.