1) Carbon dioxide is a gas, so when 
is evolved in the reaction, it appears as bubbles. The gas released extinguishes the fire and it can turn lime water milky.
2) When 
is released in a decomposition reaction we can identify by the strong pungent smell of the gas released.
3) Saturated citric acid can cause corrosion of the metal layers present in the pipes. So, before draining out any acid it is neutralized so that the pipes and other plumbing works do not get damaged leading to leaks in the drainage system.
If the soil reacts with vinegar it's ph level is higher than 6.5
A or b sorry if I’m wrong
Observation, hypothesis, experiment is the correct answer
