Answer:
a. Change of state
Explanation:
Because you will see that the state has changed
An example of erosion is the Grand Canyon, which was worn away over time by the Colorado river.
DNA bop it does not say it in my test
Answer:- Yes, strontum bromide and potassium sulfate gives a precipitate of strontium sulfate.
Explanations:- As per the solubility rules, all compounds of alkali metals are soluble.
Sulfate of most of the alkaline earth metals like Ca, Ba and Sr are insoluble.
A double displacement reaction takes place when strontium bromide and potassium sulfate are mixed and a precipitate of strontium sulfate is formed:

Note: (aq) stands for aqueous and (s) stands for solid and here it's precipitate.