A 16 cm long image of an object is formed by a convex lens on a screen placed normal to its principal axis. On moving the lens towards the screen, without changing the positions of the object and the screen, a 9 cm long image is formed again on the screen. The size of the object is:

9 cm 11 cm 12 cm 13 cm

12 cm

$y=\sqrt{y_1×y_2}$ $=\sqrt{16×9}$ $=4×3=12cm$