9   9   18   54   216   ?A.1080B.1800C.864D.1728

This is a sequence problem. Let's look at the pattern:

9, 9, 18, 54, 216, ?

First, notice that each number is a multiple of the previous one:

• 9 is the same as the first 9.
• 18 is 2 times 9.
• 54 is 3 times 18.
• 216 is 4 times 54.

So, the pattern is that each number is multiplied by an increasing integer.

If we continue this pattern, the next number should be 5 times the previous number (216).

So, 216 * 5 = 1080.

Therefore, the answer is A. 1080.