People from Asia tend to live on a vegetable and fruit diet, while eating meats low in fat such as fish. They eat very little bread-wrapped foods such as sandwiches, hamburgers, bagels, paninis, etc. Few of them suffer from obesity, and obesity for them does not increase with age. However, some immigrant families who do move to America and adopt American bread-based foods, like morning bagels and lunchtime sandwiches, do start showing signs of obesity - more weight, higher blood pressure, and higher cholesterol.
Which of the following most logically completes the argument?
Though suggestive, these facts do not establish bagels and sandwiches as the culprit in obesity, however, because _________.
genetic factors could account for the lack of increase in weight with age among such people
people eating bagels and sandwiches and living from birth in more urban societies generally have a tendency to have more weight and higher blood pressure
it is possible to have a low bagel-sandwich diet upon moving to America
there are changes in other aspects of diet when immigrants move to America
carbohydrates (the foundation for bagels and sandwiches) are a necessity for human life, and death can occur when the body is deficient in carbohydrates
On this question, I narrowed down answer choices to A and D.
A seems a reasonable explanation with some sort of scientific explanation backing up the argument.
D seems plausible too, but I can't see why this is a more suitable answer than A to complete the phrase.
Any ideas, please?