函数$y=\sin\left(\dfrac{\pi}{4}-2x\right)$的单调递减区间是（ ）.
$\text{A.}$ $\left[k\pi-\dfrac{\pi}{8},k\pi+\dfrac{3\pi}{8}\right](k\in\mathbf{Z})$
$\text{B.}$ $\left[2k\pi-\dfrac{\pi}{8},2k\pi+\dfrac{3\pi}{8}\right](k\in\mathbf{Z})$
$\text{C.}$ $\left[2k\pi+\dfrac{3\pi}{8},2k\pi+\dfrac{7\pi}{8}\right](k\in\mathbf{Z})$
$\text{D.}$ $\left[k\pi+\dfrac{3\pi}{8},k\pi+\dfrac{7\pi}{8}\right](k\in\mathbf{Z})$