The diagram illustrates the procedure of placing calcium nitrate and strontium nitrate into separate boiling tubes and then heating them. The same conditions are applied. While the reactions continue, the water containing universal indicator changes colour. Which row gives the colour change and identifies the nitrate that produces the fastest colour change?
- Agreen to blue; $\text{Ca(NO}_3)_2$
- Bgreen to blue; $\text{Sr(NO}_3)_2$
- Cgreen to red; $\text{Ca(NO}_3)_2$
- Dgreen to red; $\text{Sr(NO}_3)_2$