What is a controlled variable in an experiment? a
b
A factor that is purposely left the same.
A factor that is purposely changed and being measured.
A factor that will be observed and measured.
A factor that is purposely being changed.
С
d A factor that is purposely being changed

A factor that is purposely left the same.

Explanation:

A controlled variable should not be changed throughout an experiment or else it will affect the outcome of each individual trial.

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.

true, i don't really know what you're asking but from the info you provided im guessing the answer is true.