AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
(B) 3:1 (HCl : HNO₃)
Aqua regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1 (HCl : HNO₃).
The term aqua regia (Latin for "royal water") is mentioned in NCERT as it can dissolve noble metals like gold. The ratio 3:1 (HCl : HNO₃) is a standard fact students must memorise — note that HCl is taken in greater proportion. This is a direct recall question; no derivation needed.