An article titled "The More Pets You Meet as a Baby, the Lower Your Risk of Allergies" reports the results from a study of 1,029 children.

The incidence of allergies was 49 percent in children who had spent their first 12 months of life in a
home with no pet. This fell to 43 percent in children who as babies had lived with one pet, and
24 percent for children who had lived with three pets. Two of the children had lived with five pets—
neither of them had allergies.

Explain why it is not reasonable to conclude that being raised with more pets is the cause of the observed lower
allergy rate.

(a) It is reasonable because it would be unethical to perform an experiment that may induce allergies in
children, so we must use an observational study.
(b) It is not reasonable because children can be allergic to things besides pets, such as food items or
medications.
(c) It is reasonable because there is a clear declining trend in allergy incidence based on the number of pets
the child lived with.
(d) It is not reasonable because this was an observational study, so cause-and-effect conclusions cannot be
drawn