<prompt> Which of the following is not true about water quality estimationClostridium spores indicate recent contaminationNot more than 5 samples should have coliformsSodium thiosulfate added to neutralize chlorineColiforms must not be detectable in 100ml sample  <response>: Option aColiform organism Most commonly used bacteriological indicatesFaecal streptococci Recent faecal pollution of water.Spores of Cl. perfringence in the absence of coliform group Remote faecal contamination of water.About other optionsOption b. dTotal coliform bacteria must not be detectable in any 100 ml of sample.But, In case of large supplies, where sufficient samples are examined, coliform bacteria must not be present in 95 of samples taken throughout any 12 months period Not more than 5 samples should have Coliforms.Option cSodium thiosulfate is used to dechlorinate tap water for aquariums or treat effluent from waste water treatments prior to release into rivers.It is also used to lower chlorine levels in swimming pools and spas following superchlorination. 