<prompt> Phase I trial is done to test:SafetyEfficacyDosePharmacokinetics  <response>: Ans. D. PharmacokineticsPhase I trial is also called First in human trial. In this phase, 10-100 healthy people are enrolled to calculate pharmacokinetic data. Phase 0 trials are also done sometimes prior to phase I studies to calculate early pharmacokinetic data. Phase II and III trials usually enrol patients. Phase II trials enrol 50-100 and usually determine drug efficacy and dose ranging. Phase III trials confirm the efficacy in larger population 100-1000. Phase IV trials are also known as postmarketing studies which determine safety adverse drug reactions, adverse events, and drug-drug interactions. Even safety of long-term drug treatment can be determined in Phase IV trials which can be missed in clinical trials due to limited duration of clinical trials. 