The value of 0.01 + 0.81 + 1.21 + 0.0009 is = ?

Answer: Option D

Given expression,
$$=\sqrt{\frac{1}{100}}+\sqrt{\frac{81}{100}}+\sqrt{\frac{121}{100}}+$$      $$\sqrt{\frac{9}{10000}}$$
$$\begin{array}{rl}& =\frac{1}{10}+\frac{9}{10}+\frac{11}{10}+\frac{3}{100}\\ & =0.1+0.9+1.1+0.03\\ & =2.13\end{array}$$