Covariances of Poisson process increments

Let $\{N(t) : t \ge 0\}$ be a homogenous Poisson process with the intensity/rate $\lambda = 2$. Let $X = N(6) - N(1)$, $Y = N(5) - N(3)$, $W = N(6) - N(5)$, $Z = N(3) - N(1)$. Then which one of the following options is correct?