HEEELP How does diffusion occur across a cell membrane (where do the molecules cross the membrane)

Diffusion is one of the processes that allows this to happen. Diffusion occurs when particles spread. They move from a region where they are in high concentration to a region where they are in low concentration.

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.