Task: Question Answering
Input (English): Question: Regarding the phases of the clinical development of a drug, which of the following characteristics does NOT correspond to a clinical trial in phase 2? 
 Options:  <1> They are exploratory therapeutic studies. <2> They are performed in a large number of patients (between 100 and 1000). <3> They are used to delimit a range of therapeutic doses. <4> The informed consent of the patients is required for their inclusion in the study. <5> They are usually of short duration.
Output (English): 2