The only independent variable in this experiment is the amount of nitrogen Sarah uses. All of the other variables are dependent on other factor and processes, but Sarah controls the amount of nitrogen that she uses for each plant.
the answer is D
20 characters must be written...... Y?
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The dirt sucks up the water from the surface to go to animals and plant and then becomes groundwater.
Covalent bond radius refers to half of the distance between two singly bonded atoms of the same element ( homonuclear X-X bond) and is denoted rcov. In other words, it is defined as half the covalent bond length when the two atoms bonded are homonuclear.
This type of grouping is called clades.