How many combinations of three letters taken from letters (b, b, c, c, d,d) are possible?  Choose one:	A) 12	B) 13	C) 5	D) 6	E) 7
So 3C3 for bcd - 1 choice   2 more for dd(b,c )   2 more for bb(d,c )   2 more for cc(d,b )   total 7   Ans :7
<result>E</result>
How many combinations of three letters taken from letters (b, b, c, c, d,d) are possible?