Metabolism is
1. a measure of the hydrogen ion concentration in a solution
2. the energy required to start a chemical reaction
3. all of the chemical reactions in an organism required to sustain life
4. a chemical reaction in which the substrates trade constituent parts

3 : All of the chemical reactions in an organism required to sustain life.

Explanation: Metabolism is the process of converting food into energy form ( ATP). Metabolism is set of biochemical reactions which is completed in presence of necessary enzymes and is essential to sustain life.

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.