Which pair of substances would most likely result in the production of a gas when reacting with an acid?
O litmus and methyl orange
O base and salt
metal and carbonate
O carbon dioxide and water

Your question is not clear but if you can explain yourself i would be glad to .  just trying to : ))

Hbr dissociates to form h+ and br-ca(oh)2 dissociates to form ca2+ and 2oh-the h+ and oh- react to form waterassuming the reactants are dissolved in water, the net reaction is h+ + oh- —> h2oif you’re asked to show all components of the reaction, the complete reaction is 2hbr + ca(oh)2 —> cabr2 + 2h2o