7. (5 points) Consider the surface described by the equation z = 3+x2+2y2 -xy and the point on the surface Po = (1, 2, 10) Which one is the equation for the line tangent to the surface at Po in the direction of u = (2, 1)? (A) r(t) = (1 + 2t, 2 + t, 10 + 9t) (B) r(t) = (1 + 2t, 2 + t, 10 + 10t) (C) None of these (D) * r(t) = (1 + 2t, 2 + t, 10 + 7t) (E) r(t) = (1 +2t, 2 + t, 10 + 5t)