Sara and Juan conducted an experiment to test which soil would be BEST for growing plants.

They used all three types of soil seen in the jar: sand, silt, and clay. They also made a mixture of soil using equal parts of sand, silt, and clay. The planted bean seeds in four pots and placed the pots in the sunlight. They watered the pots every day and tracked the seed germination and plant growth.

Which of these is a control of the experiment?

A) type of soil

B) plant growth

C) time needed for germination

D) amount of water given to the seeds

D) amount of water given to the seeds

Explanation:

The controlled variable in the experiment would be the amount of water given to the seeds.

A controlled variable in an experimental investigation is a variable that remains unchanged throughout the entire duration of the experiment. It remains unchanged because a slight variation could change the outcome of the experiment and renders the result inaccurate.

In the experiment, the amount of water given to the seeds in the four pots must be constant because water represents an important factor in the growth of plants. A slight variation in the amount of water given to the pots will influence the growth of the plant. It will become difficult to determine if the variation in the growth of the plants is due to the water variation or different soil types.

The correct option is D.

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