Evaluate:  $$\sqrt{21+\sqrt{19-\sqrt{6+3}}}$$ .

Correct option is D

Given: 

$$\sqrt{21+\sqrt{19-\sqrt{6+3}}}$$ 

Solution; 

= $$\sqrt{21+\sqrt{19-\sqrt{6+3}}}$$ 

= $$\sqrt{21+\sqrt{19-\sqrt{9}}}$$ 

= $$\sqrt{21+\sqrt{19-3}}$$ 

= $$\sqrt{21+\sqrt{16}}$$ 

= $$\sqrt{21+4}$$ 

= $$\sqrt{25}$$ 

= 5