Which of the following sequences is NOT arithmetic?(A) -4, 2, 8, 14, ..., (B) 9, 4, -1, -6, ... (C) 2, 4, 8, 16,... (D)frac{1}{3},1*frac{1}{3},2*frac{1}{3},3*frac{1}{3}',...

An arithmetic sequence contain a constant common difference between each term. To find the common difference, we can subtract the first term from the second term. Doing this, we found that only C does not have a constant common difference, hence making it not an arithmetic sequence.
Let d = common difference
A) $14-8=6$
$8-2=6$
$2-(-4)=6$
$d=6$
B) $-6-(-1)=-5$
$-1-4=-5$
$4-9=-5$
$d=-5$
C) $16-8=8$
$8-4=4$
$4-2=2$
d=does not exist
D) $3\times \frac{1}{3}-2\times \frac{1}{3}=1$
$2\times \frac{1}{3}-1\times \frac{1}{3}=1$
$1\times \frac{1}{3}-\frac{1}{3}=1$
$d=1$
Result: Choice C