What is "slab-push"? can some give me one example of a slab-push structure.

*A slab push is a term given to tectonic plates that cause pressure from a down-dip motion. An example of this type of plate structure is where the Nazca plate and the South American plate meet near Peru

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.