Analysis: use the opening direction of parabola to judge the relationship between A and 0, and use the intersection of parabola and Y axis to judge the relationship between C and 0. Then, according to the symmetry axis and the intersection of parabola and X axis, the conclusion can be judged.

Solution: solution: ∫A > 0, so ① is correct;

∵ Vertex abscissa -b/2a < 0, so the vertex is not in the fourth quadrant ② error,

∵ Parabolic opening is upward, and the Y axis intersects the negative semi-axis.

Therefore, the intersection with the X axis must be one on the positive half axis and the other on the negative half axis, so ③ is correct.

So C. Comments: This question examines the determination of the sketch of quadratic function and the determination of the coefficient sign of quadratic function Y = AX2+BX+C, I don't know if it is this multiple-choice question! Call me if you have any questions!