Which of the following statements best describes how to calculate the toxicokinetic half-life using the concentration of a drug in plasma?
_____ A. Time needed for the plasma concentration to rise to 50% of its peak level immediately following exposure
_____ B. Time needed for the plasma concentration to be reduced from its peak to a level equal to 50% of the peak
_____ C. Time that the plasma concentration remains above a level equal to 50% of the peak
_____ D. Time needed for the plasma concentration to be reduced from the 50% level to below detectable limits