Given, 

$\sqrt{1000}+\frac{3.001}{4.987}of1891.992=?$

It can also be approximated as

$\sqrt{1000}+\frac{3.000}{5.000}of1900=?$

$$\begin{gathered} = \sqrt{1000}+\frac{3}{5}\times 1900 \\ = \sqrt{1000}+3\times 380 \\ = 10\sqrt{10}+1140 \\ = 1171.6 \end{gathered}$$

=1171.6 ≈ 1230

Hence, Option B is correct.