Answer :
Step 1: Identify the formula to get the surface area(S.A) of a cone
Given values include,
Diameter= 12m
Radius (r)= diameter/2= 12m/2=6m
slant height (l)=9m
The formular is given as thus,
[tex]\begin{gathered} SA=Area\text{ of the circular base +Curved suface area} \\ SA=\pi r^2+\text{ }\pi rl \end{gathered}[/tex]Area of circular base will be
[tex]\begin{gathered} \text{Area of circular base= }\pi r^2 \\ \text{Area of circular base}=\text{ }\pi\times6^2 \\ \text{Area of circular base=36}\pi m^2 \\ \text{leaving in terms of }\pi \\ \end{gathered}[/tex]curved surface area will be
[tex]\begin{gathered} \text{Curved sureface Area=}\pi rl \\ \text{curved surface area=}\pi\times6m\times9m \\ \text{curved surface area=54}\pi m^2 \\ \text{Leaving in terms of }\pi \end{gathered}[/tex]Therefore,
The surface area of the cone will be
[tex]\begin{gathered} SA=36\pi m^2+54\pi m^2 \\ SA=90\pi m^2 \end{gathered}[/tex]Hence,
The surface area of the right cone= 90πm²
Therefore the correct answer is option A