Alaboratory study using rats showed a steady increase in physical effects as the concentration of a toxic substance in their food was increased.
this suggests that

Manganese toxicity

Explanation:

The magnesium is a toxic and poisonous substance that results from a continuous exposure of the substance and the chronic exposure a lead to the psychiatric and motor disturbances as the reduction in the speed ad the mood changes, and the other behavior patterns. As magnesium is known to cause the side effects on the kidneys, and the liver function and the chances of the acute toxicity are always high. Those animals that produce offspring have a malformed body.

Answerscripps institution of oceanography; i believe this is correct plz check first good luck;

5×^2+20-15 or -(5x^2-20+15)