Total surface area of a solid hemisphere = $2\pi r^2 + \pi r^2 = 3\pi r^2$
Ratio = $3\pi r^2 : r^2 = 3\pi : 1$
Answer: (C) $3\pi : 1$
The total surface area of a solid hemisphere has two parts: the curved surface area ($2\pi r^2$) and the flat circular base ($\pi r^2$), giving $3\pi r^2$. Dividing by $r^2$ gives the ratio $3\pi : 1$. Students often forget to include the base area — that's the most common mistake here.