Fan-shaped birthday calligraphy works

∫ The bottom radius is 9 cm, and the height is 12 cm.

∴ bus cone length = 122+92= 15cm,

The radius of the bottom is 9 cm,

∴ Bottom circumference = 18πcm,

∴nπ× 15 180= 18π,

The solution is n=2 16,

The central angle of the sector paperboard is 2 16.

So choose C.