Identify a Process Within the Human Body That Affects the Efficacy

Identify a process within the human body that affects the efficacy of swallowed drugs.

A) Significant proportions of swallowed drugs are transported from the digestive system to the liver and metabolized before having any effect on the user's behavior.
B) Metabolic by-products are generally less active than the original substance, so the liver produces no active drug from inactive ones.
C) A small fraction of the drug may be metabolized outside the liver and that small amounts of most drugs are often remetabolized before excretion.
D) Cardiovascular functioning is important, because the slower the distribution of the drug to the liver, the higher the rate of metabolism will be.