A student brings each pair of chemicals together in separate test-tubes. • excess calcium $(s)$ + water $(l)$ • barium chloride $(aq)$ + strontium hydroxide $(aq)$ • calcium carbonate $(s)$ + excess hydrochloric acid $(aq)$ • magnesium sulfate $(aq)$ + barium nitrate $(aq)$ For how many of these mixtures is a white solid formed?
- A0
- B1
- C2
- D3