How many combinations of three letters taken from letters (a, b, b, c, c, d,d) are possible?
Options:
A) 4C3+4 B) 4C3+9 C) 4C3+2 D) 4C3 E) 4C3+6
So 4C3 for abcd - 4 choices   3 more for dd(b,c or a)   3 more for bb(a,c or d)   3 more for cc(a,b or d)   total 4C3+9   Ans : 4C3+9
<result>B</result>
How many combinations of three letters taken from letters (a, b, b, c, c, d,d) are possible?