Ans. is 'a' i.e., 8 days Summary of pregnancy tests (Beta HCG)TestTest sensitivity'Time takenInferencePositive onImmunological tests (Urine)Agglutination inhibition test (Latex test)0.5 - 1 IU/ml (urine)2 minutesAbsence of agglutination2 day after missed periodDirect latex agglutination test0.2 IU/ml (urine)2 minutesPresence of agglutination2-3 days after missed periodTwo-site sandwitch immunoassay (membrane ELISA/card test)30 - 50 mIU/ml (urine)4-5 minutesColour bands in control as well as test windowOn the first day of the mi ssed period (28th day of cycle)ELISA1 -2 mIU/ml2 - 4 hours 5 days before the first missed periodRadio - immunoassayBeta unit0.002 IU/ml3 - 4 hours 25th day of cycleImmunoradiometric assay (IRMA)0.05mIU/ml(serum)30 minutes 8 days after conception