Which oxide of transition metals exhibits electrical conductivity as high as that of metals?

Which of the following is a highly corrosive salt?

$Cu_2Cl_2$ with $HCl$ in the presence of oxidizing agents gives:

The conversion of pig iron to steel frequently requires the addition of
$(I)$ oxygen or iron oxide
$(II)$ transition elements
$(III)$ inner transition elements
$(IV)$ silica

Which from the following alloys is used in gas turbine engines?

$ZnO \cdot CoO$ is called