Answers
-Worldwide sea level increased
-river plains drowned
Explanation
Glaciers are large blocks of ice and with all the ice melting the water levels rose worldwide. (Correct Answer)
When sea levels rose it caused river plains to be flooded. (Correct Answer)
Glaciers are made from freshwater so when they melt the salinity in estuaries does change. (Not a correct Answer)
Erosion definitely affected river valleys. Alpine glaciers create valleys and even help erode valleys. With Alpine glaciers melting this slows the process of that erosion and with them melting the river valleys will eventually flood. (Not a correct Answer)
I hope this helps!