What is known as Thomas slag?

Among the reactions $(a) - (d)$,the reaction$(s)$ that does/do not occur in the blast furnace during the extraction of iron is/are:
$(a)$ $CaO + SiO_2 \rightarrow CaSiO_3$
$(b)$ $3 Fe_2O_3 + CO \rightarrow 2 Fe_3O_4 + CO_2$
$(c)$ $FeO + SiO_2 \rightarrow FeSiO_3$
$(d)$ $FeO \rightarrow Fe + \frac{1}{2} O_2$

Explain the following:
$(a)$ $CO_2$ is a better reducing agent below $710 \ K$ whereas $CO$ is a better reducing agent above $710 \ K$.
$(b)$ Generally,sulphide ores are converted into oxides before reduction.
$(c)$ Silica $(SiO_2)$ is added to the sulphide ore of copper in the reverberatory furnace.
$(d)$ Carbon and hydrogen are not used as reducing agents at high temperatures for certain metals.
$(e)$ Vapour phase refining method is used for the purification of $Ti$.

The correct option$(s)$ related to the extraction of iron from its ore in the blast furnace operating in the temperature range $900-1500 \ K$ is(are):
$(A)$ Limestone is used to remove silicate impurity.
$(B)$ Pig iron obtained from blast furnace contains about $4 \%$ carbon.
$(C)$ Coke $(C)$ converts $CO_2$ to $CO$.
$(D)$ Exhaust gases consist of $NO_2$ and $CO$.

Identify the alloy containing a non-metal as a constituent in it.

The statement that is $NOT$ correct is: