The two sentences contradictory statements in the key are called

Couplet

Explanation:

Taxonomic Key

A taxonomic is a tool used by scientists to identify and organism. It consists of a series of contradictory statements or questions that eventually lead to the classification of the organism. Choosing the appropriate option in each of the statements gives a detailed description of an organism's characteristics that help in its identification.

This pair of contradictory statements is called a couplet and each statement in a couplet is called a lead.

For a plant, the follow contradictory statements will be called a couplet:

1. Seed colour: Black

1. Seed colour: white

2. Plant height: Tall

2. Plant height: short

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.