Acetaminophen Stock Standard Solution (this is the initial solution from which the working standard is OBTAINED): Weigh 250.0mg of acetaminophen reference standard and 32.5mg of caffeine reference standard into a 250mL volumetric flask. Add 75mL of Solvent Mixture and shake (or/and sonicate) until the standards dissolve. Add Solvent Mixture to volume. Mix! Acetaminophen Working Standard Preparation (this preparation is injected into the HPLC): Transfer 5.0mL of the Standard Stock Solution and 3.0mL of the Internal Standard Solution into a 50mL vol. flask and dilute to volume with Solvent Mixture. Mix! Question: Above are the stock standard solution and the working standard preparation for the assay of acetaminophen tablets. The method requires that you prepare a calibration standard and a check standard for injection into the HPLC. Note: The purpose of the check standard is to 'check' or ascertain the accuracy of your calibration standard. If both check and calibration standards gave the similar responses, then the analyst has great confidence that the calibration standard was prepared correctly. Select the correct answer(s). 1. I must prepare one stock standard solution for my calibration standard and another stock standard solution for my check standard. 2. I must prepare and use the same stock standard solution for both calibration standard and check standard. 3. I must prepare and use the same working standard preparation for both calibration and check standards. 2 and 3 1 3 1 and 2 2 1 and 3