#### Answer

Not an arithmetic sequence.

#### Work Step by Step

In order for a sequence to be arithmetic, the difference of all consecutive terms must be constant.
Here: $a_2-a_1=-5-2=-7$
$a_3-a_2=-11-(-5)=-6$
$a_4-a_3=-16-(-11)=-5$
Thus we can see that the difference is not constant, thus it is not an arithmetic sequence.