Bmat 2019 q 2 chem

can someone explain?
answer: C

  1. CaCO3 is a base, and the question says that water alone doesn’t remove it; therefore, an acid must have reacted with it. So, answer 1 is correct so far.

  2. Since its an acid+base reaction, the products are (in this case) H2O, CO2, and a salt. Hydrogen isn’t the reason for the fizzing, but CO2 (g) is.

  3. The salt (the solid limescale)is more soluble than CaCO3 because it started to disappear as the reaction proceeded, and CaCO3 couldn’t be dissolved in water alone.

Therefore, the answer must be C.
I’m unsure why statement 3 is incorrect, but the only answer containing statements 1 and 4 is C.