Which statement accurately describes the relationship between the brain and addiction?
a. normal activities produce heightened responses once receptors are reduced. b. a higher amount of addictive chemicals are needed to get the same high when fewer receptors are present. c. the brain reacts to excessive dopamine levels by increasing the number of dopamine receptors. d. all drugs act on dopamine synapses in the same way.

 C. The brain reacts to excessive dopamine levels by increasing the number of dopamine receptors. 

The statement accurately describes the relationship between the brain and addiction. There is a significant link between neurotransmitters and its influence on the activity and the emotion that we feel towards that set of activity. When there is an abnormal or disoriented amount of neuro-chemicals then it would cause some dysfunctional responses on the activity. 

It should be cryosphere and hydrosphere

Digestion because it removes waste