We know, the total surface area of a right circular cone =πr(r+l).
Given, diameter of the cone =14 cm.
Then, radius r=d2=142=7 cm.
Also, height h=24 cm.
Then, slant height l=√h2+r2
⇒l=√242+72
⇒l=25 cm.
Now substitute the value in above equation, we have,
the total surface area =π×7(7+25)
=227×7(32)
=704 cm2.
Therefore, option C is correct.