Given $P(x)=x^{4}+a x^{3}+b x^{2}+c x+d$ such that $x=0$ is the only real root of $P^{\prime}(x)=0$. If $P(-1)<P(1)$, then in the interval $[-1,1]$ $[2009$
(A) $P(-1)$ is the minimum and $P(1)$ is the maximum of $\mathrm{P}$
(B) $P(-1)$ is not minimum but $P(1)$ is the maximum of $\bar{P}$
(C) $P(-1)$ is the minimum and $P(1)$ is not the maximum of $P$
(D) neither $P(-1)$ is the minimum nor $P(1)$ is the maximum of $P$