Which of the following is not correct?

Question

(a) $SiO_2$ used as acid flux

(b) The distance between the layers in graphite is $3.35 \times 10^{-3}\;cm$

(c) $SiO_2$ reacts with $Na_2CO_3$ and liberates $CO$

(d) The hybridisation of C in graphite is $sp^2$