Task: Text Categorization
Input (English): Question: In a determination of the activity of an enzyme, the depletion of the substrate: 
 Options:  <0> It is essential for most trials. <1> It may give falsely low results in sera with high enzymatic activity. <2> It occurs when the reagent is finished. <3> It occurs due to a defect in the spectrophotometer. <4> It can lead to falsely elevated results in sera with high enzymatic activity.
Output (English): pharmacology