The sum of first n odd natural numbers in

Answer: Option C

1, 3, 5, 7, ........ are n odd numbers
Where a = 1, and d = 2
$$\begin{array}{rl}& \therefore S_n=\frac{n}{2}\left[2a+\left(n-1\right)\right]\\ & =\frac{n}{2}\left[2\times 1+\left(n-1\right)\times 2\right]\\ & =\frac{n}{2}\left[2+2n-2\right]\\ & =\frac{n}{2}\times 2n\\ & =n^2\end{array}$$