The best fuel gas when used with oxygen is:: (A) Hydrogen, (B) Natural gas, (C) Propane, (D) Acetylene
Answer is C. Propane
Of the fuel gases, the best choice is propane. Butane, which is more readily available in some parts of the world, has a similar flame temperature and heat content as propane. Both  propane  and  butane have the advantage of being relatively pure compounds; therefore, they are uniform in quality are virtually water-free, and burn cleanly (provided that the torch flame is properly adjusted).