A

Aqua regia is prepared by mixing conc. HCl and cone. $$HNO_3$$ in 3 : 1 (v/v) ratio

B

Reaction of gold with aqua regia produces an anion having Au in +3 oxidation state

C

Reaction of gold with aqua regia produces $$NO_2$$ in the absence of air

D

The yellow colour of agua regia is due to the presence of NOCl and $$Cl_2$$