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Looking at the information given in the description, the experiment is testing for the effects of the different salts on the growth of the plants.
This means that the type of salt is the independent variable, or the variable being manipulated and tested.
To ensure fair results, some parts of the experiment would need to be kept the same, which is the control. The only answer choice that makes sense in this instance is A. water.
Polar covalent bond- a bond where atoms are unevenly shared due to a larger difference in electronegativity of the bonded elements.
Non-polar covalent bond- These are bonds between elements with a low difference in electronegativity. Electrons are shared equally in these bonds between the elements.
Ionic bonds- have such large difference in electronegativity that they take/give electrons to the element they are bonded to. They do not share electrons at all. Bonds between a non-metal and a metal.
