Which explains why the sequence 216, 12, two-thirds, … is arithmetic or geometric.

A. The sequence is geometric because it decreases by a factor of 6.
B. The sequence is arithmetic because it decreases by a factor of 6.
C. The sequence is geometric because it decreases by a factor of start fraction 1 over 18 end fraction.
D. The sequence is arithmetic because it decreases by a factor of start fraction 1 over 18 end fraction.

C. The sequence is geometric because it decreases by a factor of 1/18.

The correct answer is:

C. The sequence is geometric because it decreases by a factor of start fraction 1 over 18 end fraction.