Given expression is [tex]7 \sqrt{50x^{15}y^{21}}[/tex] where x and y are non negative.
Now we have to simplify this to find the correct matching choice.
[tex]7 \sqrt{50x^{15}y^{21}}[/tex]
[tex]=7 \sqrt{25*2x^{15}y^{21}}[/tex]
[tex]=7 \sqrt{25*2x^{14}*xy^{20}*y}[/tex]
[tex]=7*5x^{7}y^{10} \sqrt{2*x*y}[/tex]
[tex]=35x^{7}y^{10} \sqrt{2xy}[/tex]
Which best matches with choice D.
Hence final answer is [tex]35x^{7}y^{10} \sqrt{2xy}[/tex] .