设 $M=\iint_{|x|+|y| \leqslant 1}(x+y)^3 \mathrm{~d} \sigma, N=\iint_{x^2+y^2 \leqslant 1} \cos x^2 \sin y^2 \mathrm{~d} \sigma, P=\iint_{x^2+y^2 \leqslant 1}\left(\mathrm{e}^{-x^2-y^2}-1\right) \mathrm{d} \sigma$, 则必有
$\text{A.}$ $M>N>P$.
$\text{B.}$ $N>M>P$.
$\text{C.}$ $M>P>N$.
$\text{D.}$ $N>P>M$.