单项选择题
A.D3DXVec3Length()B.D3DXVec3Normalize()C.D3DXVec3Dot()D.D3DXVec3Cross()
A.D3DXVECTOR2B.D3DXVECTOR3C.D3DXVECTOR4D.D3DXVECTOR
A.DrawPrimitive()B.DrawIndexedPrimitive()C.DrawSubset()D.Draw ()