If $\begin{pmatrix} \frac{1+i}{1-i} \end{pmatrix}^x=1$, then:

Question

( A ) $x=2n+1$, where $n$ is any positive integer
( B ) $x=4n+1$, where $n$ is any positive integer
( C ) $x=4n$, where $n$ is any positive integer
( D ) $x=2n$, where $n$ is any positive integer