22) B

A higher concentration of acid indicates that the rate of reaction would be faster than the original experiment.

Only B and A fit this condition so we can eliminate C, D and E.

Since the amount of acid present is the same (100cm³ x 1 mol/dm³ = 50cm³ x 2mol/dm³), the overall amount of carbon dioxide produced would be the same as the initial experiment. Therefore, B is the answer.