Let side of square $=x$
Given, percentage change in side $=6 \%$
$$
\frac{d x}{x} \times 100=6 \%
$$

We have, $A=x^2$
Differentiate w.r.to ' $x$ '
$$
\frac{d A}{d x}=2 x \Rightarrow d A=2 x d x
$$
Dividing by $x^2$ on both sides
$$
\begin{aligned}
\frac{d A}{x^2} & =2 \cdot \frac{x d x}{x^2} \\
\frac{d A}{A} & =2 \frac{d x}{x}
\end{aligned}
$$
$$
\left[\because A=x^2\right]
$$
Now, multiply by 100
$$
\frac{d A}{A} \times 100=2 \times\left(\frac{d x}{x} \times 100\right)
$$
$$
\begin{aligned}
\text { Percentage change in Area } & =2 \times 6 \% \quad \text { [from Eq. (i)] } \\
& =12 \%
\end{aligned}
$$
Hence, option (2) is correct.