A person buys twelve packets of VANISH detergent. Each packet contains one coupon, which bears one of the letters of the word VANISH. If he shows all the letters of the word VANISH, he gets one free packet. If he gets exactly one free packet, then the number of different possible combinations of the coupons is
(A) 18C6 – 17C6
(B) 11C5 – 1
(C) 17C5
(D) 461
