Explanation

(c)
Given,$\frac{\delta r}{r} \times 100 = 2 \Rightarrow \delta r = \frac{2r}{100}$
Surface area, $\ \ S = 4\pi r^{2}$
$\delta S = 4\pi 2r.\delta r$
$8\pi r.\frac{2r}{100} = \frac{16\pi r^{2}}{100}$
Now percentage error in surface area
$\frac{\delta S}{s} \times 100 = \frac{16\pi r^{2}}{100} \times \frac{1}{4\pi r^{2}} \times 100 = 4\%$