The general form of the geometric sequence is 
, where a sub n is the number term you're looking for (we're looking for the tenth term). a sub 1 is the first term in the sequence (ours is -6), r is the common ratio, and n-1 is the numbered term you're looking for minus 1. Our formula then looks like this: 
. Simplify it to 
. Take 2 to the 9th power then multiply it by -6 to get -3072. C is your answer.