It can either be a convex mirror or concave mirror. It depends upon the position of the object. u is always negative so in order to get magnification positive v must be negative. If the object is kept between pole and the focus of the mirror, then it will form a virtual image behind the mirror and v will be +.

**Real and Virtual Images**

When light rays pass through a lens or reflect off a mirror, they create an image. This image can be classified as either real or virtual.

1. **Real Images:** A real image is formed when light rays actually converge at a specific point after passing through a lens or reflecting off a mirror. This image can be captured on a screen and is always inverted.

2. **Virtual Images:** A virtual image is formed when light rays appear to diverge from a specific point after passing through a lens or reflecting off a mirror. This image cannot be captured on a screen and is always upright.

**Positive Magnification**

The magnification of an image indicates the size and orientation of the image formed by a lens or mirror. It can be positive or negative.

When the magnification has a positive sign, it means the image formed is upright or erect. This indicates that the image is virtual.

**Concave Mirror**

A concave mirror is a mirror with a curved reflective surface that bulges inward. It can form both real and virtual images, depending on the position of the object relative to the mirror.

When the object is placed beyond the focal point of the concave mirror, a real inverted image is formed. This is because the light rays converge at a specific point.

However, when the object is placed between the focal point and the mirror, a virtual erect image is formed. This is because the light rays appear to diverge from a specific point.

**Explanation**

In the given question, if the magnification has a positive sign, it means the image formed is virtual and erect. Since the mirror mentioned is a concave mirror, the only option that matches these criteria is option C - virtual and erect.

Therefore, when the magnification has a positive sign, the image formed by the concave mirror must be virtual and erect.

The image will form behind the mirror and hence it will be virtual and erect as it is possible only when the object is placed between pole and focus of concave mirror