Given,

$\frac{3}{5} \text{of\hspace{0.17em}}\frac{7}{19}\text{\hspace{0.17em}of\hspace{0.17em}}\frac{15}{28}\mathrm{of} 543=?$

It can be approximated as

$\frac{3}{5} \text{of\hspace{0.17em}}\frac{7}{20}\text{\hspace{0.17em}of\hspace{0.17em}}\frac{15}{30}\mathrm{of} 550=?$

$$\begin{gathered} \begin{array}{l}=\frac{21}{100}\times \frac{1}{2}\times 550=?\text{\hspace{0.17em}\hspace{0.17em}or\hspace{0.17em}}\frac{20}{100}\times \frac{550}{2}=?\\ \end{array} \\ \text{ ?= }\frac{{\displaystyle 550}}{{\displaystyle 5\times 2}} \end{gathered}$$ 

= 55 ≈ 50

Hence, Option D is correct.