Chlorine is used for disinfection at a water treatment plant that treats 0.20 m3 /s of reservoir water. when exposed to chlorine, the apparent inactivation rate (k*=kcn ) of giardia (a protozoan) is 0.53 min-1 , while the inactivation rate of e. coli (a bacteria) is 2.8 min-1. between giardia and e. coli, giardia is considered the primary pathogen of concern. based on the information given above, why is this the case?