Which statement about the use of independent variables in controlled experiments is correct? 1.
A different independent variable must be used each time an experiment is repeated.
2.
The independent variables must involve time.
3.
Only one independent variable is used for each experiment.
4.
The independent variables state the problem being tested.

Explanation:The independent variables must involve time.

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igneous rock formed from below the surface would have more crystals because

answer: because magma cools more slowly than lava

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.