Why do nations establish trade barriers?

Awatershed is a piece of land that drains water into a particular stream, lake, or river. which of the following factors often negatively impacts the water quality in a watershed? a.) wetlands b.) pollution c.) irrigation d.)rainfall

Aletsch glacier is the largest glacier in switzerland and the largest found in the alps, a mountain range which extends from monaco in the east to slovenia in the west. currently, the aletsch glacier is retreating. under what circumstances would this glacier see growth instead of retreat? a decline in plate tectonics across the mountain range annual snowfall that exceeds yearly losses an increase in ablation in the southern valleys a rise in temperatures to that of a mediterranean climate

Heyi am new to are you all americans? ( just want to know , i don't mean any offence ) ?