To solve this question, the user needs to identify the pattern in the given series of numbers.
The first number is 9, and each subsequent number is obtained by multiplying the previous number by a multiple of 2.
9 x 2 = 18
18 x 4 = 72
72 x 6 = 432
432 x 8 = 3456
Therefore, the missing number in the series is obtained by multiplying 432 by 8, which equals 3456.
So, the Answer is: C. 3456