An excess of potassium ions makes KCl crystal appear violet or liliac in colour since:
(A) Some of the anionic sites are occupied by an unpaired electron
(B)Some of the anionic sites are occupied by a pair of electrons
(C) There are vacancies at some anionic sites
(D) F-centres are created which impart colour to the crystals.

Choose the correct answer from the options given below :
(