A dentist observes and checks the patient’s teeth using a mirror with an 8 cm radius. In order for the hole to be seen clearly by the doctor, what is the distance between the patient’s teeth and the mirror?
A. less than 4 cm in front of a concave mirror
B. less than 4 cm in front of a convex mirror
C. more than 4 cm in front of the concave mirror
D. more than 4 cm in front of the convex mirror