There are numbers $$a_{1}, a_{2}, a_{3}, ....,an$$ each of them being +1 or -1. If it is known that $$a_{1}a_{2} + a_{2}a_{3} + a_{3}a_{4} +⋯ a_{n−1}a_{n} + a_{n}a_{1} + = 0$$ then

A

n is a multiple of 2 but not a multiple of 4

B

n is a multiple of 3

C

n can be any multiple of 4

D

The only possible value of n is 4