premise: rate is a kind of measure of speed sent2: tree roots decrease / reduce soil erosion sent3: planting trees increases the number of trees in an environment sent4: planting tree is a kind of human action sent5: if something decreases something else then increasing that something will decrease that something else sent6: roots are a part of a plant / tree sent7: to slow / to slow down decreases speed.
hypothesis: the brain and the spinal cord and the nerves combine to form an organ system