Answer:
reaction 1 and reaction 4 both are decomposition reactions
while reaction 2 is double displacement reaction and reaction 3 and 5 are combination reactions
It's usually water and a type of salt take the reaction between hydrochloric acid and sodium hydroxide HCl(aq)+NaOH(aq) yeilds NaCl(aq) and H2O(l)
I’m guessing it would be A because the river discharge tends to gather near coastlines where the river ends
