This part of the electromagnetic spectrum produces heat and with special equipment can locate people at night infrared waves microwaves x-rays gamma waves

a) The independent variable is the variable which is being taken as the source of an observation. It is the variable which is unaffected (changed) by other factors in the experiment

Here the independent variable is the acidity (concentrations) of the watering solutions

b, The control in the experiment is the plant group which are not administered the treatment of the experiment, such that they are kept the same through out to aid in validation of the correlation between the dependent and the independent variables

The control in the experiment are the group of 20 plants that received neutral water

c. A valid hypothesis is that there is no difference in the level of growth of a plant grown in acid rain and one grown with natural water

d. Limestone is composed of calcium carbonate, which is an alkaline that dissolves in water to form a basic solution that neutralizes the effect of the added acid such that it will invalidate the correlation of the level of plant growth with exposure to acid rain

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