`C` and `Si` both have same lattice structure, having `4` bonding electrons in each. However, `C` is insulator whereas `Si` is intrinsic semiconductor. This is because
A. in case of C the valence band is not completely filled at absolute zero temperature.
B. in case of C the conduction band is partly filled even at absolute zero temperature.
C. The four bonding electrons in the case of C ile in the second orbit, whereas in the case of Si they lie in the third.
D. The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.