单项选择题

曲面3x2+y2+z2=12上点M(-1,0,3)处的切平面与平面z=0的夹角是( ).
A.π/6
B.π/4
C.π/3
D.π/2

A.
A.π/6
B.π/4
C.π/3
D.π/2