【单选题】设y=3x^5+7x^3+2x^2+9x+12,欲求y的一阶导数和y = 0的所有根,并求x =[-4,4]区间y的函数值, 且间隔0.5计算一个值,则以下哪个程序正确( )
A.
a=[3,0,7,2,9,12] y1=polyder(a) r=roots(a) y=3* x^5+7* x^3+2* x^2+9* x+2 plot(x,y)
B.
a=[3,7,2,9,12] y1=polyder(a) r=roots(a) x= -4:0.5:4 y=3* x.^5+7* x.^3+2* x.^2+9* x+2 plot(x,y)
C.
a=[3,0,7,2,9,12] y1=polyder(a) r=roots(a) x= -4:0.5:4 y=polyval(a,x)
D.
a=[3,7,2,9,12] y1=polyder(a) r=roots(a) x= -4:0.5:4 y=polyval(a,x)