Final answer:
The best definition of drug tolerance is the need for increasing doses of a drug to achieve the same effect. It is associated with physical dependence and can lead to increased risk of overdose and death.
Step-by-step explanation:
The best definition of drug tolerance is B) The need for increasing doses of a drug to achieve the same effect. Tolerance occurs when a drug user requires more and more of a given drug in order to experience the same effects of the drug that were previously achieved with smaller doses. It is closely related to physical dependence, where the body adapts to the presence of a drug, and cessation of drug use results in withdrawal symptoms. This has to be distinguished from psychological dependence, which refers to drug craving and is more about the emotional need for a drug.
Drug tolerance can lead to increased drug consumption and raises the risk of overdose and potentially death, as the user continually attempts to reach the same high or effect that was initially experienced. This is an important concept in the field of addiction, dependence, and rehabilitation.