You've made the hypothesis that the less rainfall a cactus plant gets, the taller it will grow, since cactuses like dry conditions. what is one thing that u should control in an experiment designed to test this hypothesis? a) the height of the cactus plant b) the hours of sunlight the cactus plants gets c) the number of cactus plants in the experiment d) the amount of rain falling on the cactus plants

The amount of rain falling on the cactus plants.

Option C

Explanation:

Here, the independent variable is the amount of rain that makes the cactus plant grow taller. Control is treated the same as all the rest of the samples, except that it is not exposed to variables that are influenced.  

In most experiments, it is important to perform a trial with the independent variable, at a special locale for comparison with the other trials.

The control group consists of all trials where the independent variable is left in its natural state. These trials provide a basis for comparison and ensure that any changes observed in the height of cactus plant are in fact caused by the amount of rain.

d.

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