Carbon, silicon and germanium have four valence electrons each. At room temperature the appropriate statement is
(A) The number of free electrons for conduction is significant only in Si and Ge but small in C
(B) The number of free conduction electrons is significant in C but small Si and Ge
(C) The number of free conduction electrons is negligibly small in all the three.
(D) The number of free conduction electrons is significant in all the three.