Which of the following, if true, most seriously weakens the argument? A. There are many different strains of the E. coli bacteria, and only some of these strains are harmful. B. Some types of bacteria found in sewage are neither disease-causing nor difficult to detect directly. C. Some of the types of bacteria found in sewage along with E. coli are not harmful to people unless the bacteria are ingested in large quantities. D. E. coli dies out much more quickly than some of the more harmful bacteria found in sewage and then can no longer be easily detected. E. Some of the types of bacteria found in sewage along with E. coli reproduce at a slower rate than E. coli.