Which pair of substances would most likely result in the production of a gas when reacting with an acid?

The choices can be found elsewhere and as follows:

litmus and phenolphthalein

soluble metal salt and carbon dioxide

acids and water

hydrogen ions and soaps

I think the correct answer is the second option. The pair of substances that would most likely result in the production of a gas when reacting with an acid would be soluble metal salt and carbon dioxide.