In a study of more than 8,000 people using ten beaches on two of the Great Lakes, ecologists from the University of Toronto determined that the rate of respiratory and gastrointestinal illness among people who had been swimming was 69.6 per 1,000, whereas the respiratory and gastrointestinal illness rate among those who had not been swimming was only 29.5 per 1,000.
Which of the following conclusions can be most properly drawn from the data above
A．People tend to underestimate the risks of swimming in these lakes.
B．Respiratory and gastrointestinal illnesses occur at a higher rate as a result of swimming in either of these lakes than they do as a result of swimming in any other lake.
C．Illnesses of kinds other than respiratory and gastrointestinal are not likely to be associated with swimming in either of these lakes.
D．The association between swimming in these lakes and respiratory and gastrointestinal illness is some evidence for a causal relationship between them.
E．(E) A large percentage of the people who swim in these lakes are immune to the diseases that swimming may cause.