The correct option is C It turns milky white
When sodium hydrogen carbonate (NaHCO3) is heated above 80°C, it begins to decompose forming sodium carbonate (Na2CO3), water and carbon dioxide.
2NaHCO3(s)→Na2CO3(s) + CO2(g) + H2O(g)
When you pass carbon dioxide through limewater
(Ca(OH)2), it turns milky because calcium carbonate (CaCO3), an insoluble white solid precipitates out of the solution.
Ca(OH)2(aq)+CO2(g)→CaCO3(s)+H2O(l)