Theoretical volume of oxygen required for complete combustion of 1Nm3 of acetylene, in oxy-acetylene welding is ______________ Nm3 ?

Theoretical volume of oxygen required for complete combustion of 1Nm3 of acetylene, in oxy-acetylene welding is ______________ Nm3 ?

A. 0.5
B. 1
C. 1/3
D. 2.5