Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate?

(a) The number of free electrons for conduction is significant only in Si and Ge but small in

(b) The number of free conduction electrons is significant in C but small in Si and Ge

(c) The number of free conduction electrons is negligibly small in all the three

(d) The number of free electrons for conduction is significant in all three