A concave mirror has a focal length of $20\ \text{cm}$. A small object is placed on its axis at the four distances in List-I. Match each with the image it forms, described in List-II. List-I (Object distance from the mirror) A. $10\ \text{cm}$ B. $30\ \text{cm}$ C. $40\ \text{cm}$ D. $60\ \text{cm}$ List-II (Image formed) I. Real, inverted, half as large, $30\ \text{cm}$ in front II. Real, inverted, twice as large, $60\ \text{cm}$ in front III. Real, inverted, same size, $40\ \text{cm}$ in front IV. Virtual, erect, twice as large, $20\ \text{cm}$ behind