Ans. is 'a' i.e., 0 [Ref: K D Tripathi 7th/ep. 73 - 75, style="font-size: 1.04761904761905em; font-family: Times New Roman, Times, serif; margin: 0 0 8pt 4px; text-indent: 0; text-align: left">Phase 0 - Microdosing strategy in clinical trialso Drug development is an activity that is long, complex and expensive.o In 2004, attrition in the drug development paradigm prompted the US Food and Drug Administration (FDA) to introduce its "Critical Path" document, which highlighted the serious discordance between major scientific advances and limited drug development process.o One issue addressed was that of microdosing.o The concept of microdosing involves the use of extremely low, nonpharmacoiogically active doses of a drug to define the pharmacokinetic profile of the medication in human subjects.o Microdosing, thus, appears as a new viable concept in the "toolbox' of the drug development activity.o It is included in the phase 0 of the drug clinical trial.