Agroup of scientists are studying the effects of different fertilizers on the growth of pea plants. they began their study with 10 pea plants. they gave each plant a different type of fertilizer and tracked their growth over a period of 2 months. the results of this experiment weren’t considered valid by other scientists because there was no control group. which of the following represents an appropriate control group for this experiment? a. a group of plants that’s not subjected to any fertilizer b. a group of plants that’s subjected to one fertilizer c. a group of plants that’s subjected to all types of fertilizers d. a group of plants that’s subjected to two fertilizers

A. A group of plants that’s not subjected to any fertilizer

Explanation:

In a scientific experiment, a control group is the group that did not receive any of the treatments evaluated in the experiment.

In the experiment shown in the question above, the group of scientists wanted to test the effects of different fertilizers on the growth of 10 pea plants. Each fertilizer represents a treatment that will be tested on the plants, in which case the control group would be a group of plants that were not submitted to any fertilizer.

The control group is important because it serves as a reference standard for the evaluation of variables in other treatments. Without the control group, it is not possible for the experiment to have a credible result.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

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