Which of the following is true regarding the sequence below? 7/12,1/6,-1/4,-2/3
1) the sequence is arithmetic because there is a common difference of -5/12
2) the sequence is not arithmetic because there is a common difference of 1
3) the sequence is not arithmetic because there is no common difference between the values of n
4) the sequence is not arithmetic because there is no common difference between the values of an