Explanation:

- When an object is placed at infinity in front of a concave mirror, light rays from the object are nearly parallel to the principal axis.

- ?? Option 1: A real and inverted image is formed at the focal point. This is correct because the parallel rays converge at the focal point of the mirror, forming a real image.

- Option 2: A virtual and inverted image cannot be formed at the focal point with a concave mirror. Virtual images with concave mirrors are erect.

- Option 3: A real and erect image cannot be formed at infinity. A concave mirror forms real images at the focal point when the object is at infinity.

- Option 4: A virtual and erect image would not be formed at the focal point. Virtual images form behind the mirror.