Task: Question Answering
Input (English): Question: The maximum urinary excretion of a drug refers to: 
 Options:  <1> The maximum concentration of unchanged drug in urine. <2> The maximum speed at which the drug can be excreted unchanged by urine. <3> The amount of urine collected after 7 biological half-lives after the administration of the drug. <4> The total amount of drug that is excreted unaltered in urine after the administration of a certain dose. <5> The amount of unchanged drug recovered in urine at 24 hours after the administration of a certain dose.
Output (English): 4