The correct answer is (d) Cupola furnace melting
The explanation is: Various melting methods are used for melting of titanium metal. For example, induction, vacuum arc and electron beam melting, in which vacuum arc and electron beam melting methods are widely used, though efforts are made continuously for producing other different methods to gain better control on melting and to have better utilization of scrap materials. And cupola furnace is basically used for melting iron alloys.