Answer: B — Between pole and focus of the mirror.
When the teeth are placed between the pole and focus of a concave mirror, the image formed is virtual, erect, and enlarged, allowing the dentist to see a magnified image of the teeth.
From Table 9.1 (Chapter 9): when an object is placed between P and F of a concave mirror, the image is virtual, erect, and enlarged. This is the only position that gives a magnified image — which is why dentists use concave mirrors held close to the teeth. At focus (A), no image forms; between F and C (C), image is real and inverted; at C (D), image is same size. Examiners expect you to recall the table directly.