How are elements that are heavier than hydrogen spread throughout the universe

Elements that are heavier than hydrogen are spread throughout the universe only during a supernova explosion. It is an explosion of the stars when the star reaches its death stage. When the star is alive, the gravity of its core squeezes lighter atoms like hydrogen to make heavier atoms like carbon and helium.

answer: tributaries flow into rivers.

wetland is a biome that develops when the water gets accumulated in a land exhibiting a huge depression. these form either seasonally or permanently. the water in the wetland comes from rivers, lakes, ocean, flood, rain or other sources. the wetlands includes mangroves, marshes and peatland.

tributaries flow into the rivers develops a wetland because such water will get deposited in the depression and will restrict the original flow of tributary water. hence, water with low drainage current combines with the river water.