Answer:
(a)Common Difference

(b)Not an arithmetic sequence.
Explanation:
An arithmetic sequence is a sequence in which the next term is obtained from the previous term by the addition of a common constant.
(a)Given the sequence:

Clearly, this is an arithmetic sequence and the common difference is

(b)Given the Sequence:
-3, -7, -10, -14 …
-7-(-3)=-7+3=-4
-10-(-7)=-10+7=-3
-14-(-10)=-14+10=-4
This is not an arithmetic sequence as the constant term is not the same all true.