I believe the primary determinant of basal metabolic rate is the Lean Body Mass. Basal metabolic is the rate of energy expenditure per unit time by animals at rest. It comprises the processes that the body requires to function. It is the amount of energy per unit time that a person need to keep the body operational at a state of rest.
Crossing over? That involves the random exchange of chromosomes.
As for this problem, the most probable answer and the most likely answer for this one would be D. the effect of pesticides on organisms in the environment.
A toxicologist would only study about chemicals and their effect on organisms in the environment. Pesticides are chemicals made to combat organisms that aren't wanted particular parts of the environment such as crops and rice field. These pesticides don't just affect those organisms that are targeted, but even the users and other organisms that may have come in contact with pesticides.
Sun the answer is the sun
