Slant height $l = \sqrt{r^2 + h^2} = \sqrt{7^2 + 24^2} = \sqrt{49 + 576} = \sqrt{625} = 25$ cm
CSA of cone $= \pi r l = \dfrac{22}{7} \times 7 \times 25 = 550$ cm²
Answer: C — 550 cm²
The key step is finding slant height $l$ using $l = \sqrt{r^2 + h^2}$ before applying the CSA formula $\pi r l$. Students often mistakenly use height instead of slant height — always compute $l$ first. Here $r = 7$, $h = 24$ gives the Pythagorean triple 7-24-25.