<prompt> Phase II in a clinical drug trial isHuman pharmacology and safetyTherapeutic exploration and dose rangingTherapeutic comparisonPost marketing surveillance.  <response>: Ans. is b i.e., Therapeutic exploration and dose ranging Summary of clinical tarilsPhaseNameConducted onBlinding and controlPurposeIHuman pharmacology and safetyHealthy volunteers 20-100OPEN LABEL No bliniding To know maximum tolerable dose MTD. Safety and tolerability.IITherapeutic exploratory100-150Patients homogenous populationSingle blindControlled To establish therapeutic efficacy. Dose ranging and ceiling effect.IIITherapeutic confirmatoryUpto 5000 patients from several centres heterogenous populationDouble blindRandomizedControlled To confirm therapeutic efficacy. To establish the value of drug in relation to existing therapy.IVPost marketing surveillanceLarge number of patients being treated by practicing physicians To konwn rare and long-term adverse effects Special groups like children, pregnancy etc can be tested. 