Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that hest fits each of the numbered blanks.

(25) _______ in the past scientists have looked at things such as diet and lifestyle for

an explanation of long life, these days they are investigating genetics. One such researcher is Eric Topol, who says, “There must be genes that explain why these individuals are protected from the aging (26) _______.” 

The new research into long life looks at groups of people who have a genetic connection. For example, one group of interest lives in Ecuador. In one area of the country there are a number of people with the same (27) _______ condition. it's called Laron syndrome. The condition mea ns that they don't grow to more than about one metre, but it also seems to give them protection (28) _______ cancer and diabetes. As a result, they live longer than other people in their families. Meanwhile, on the Hawaiian island of Oahu, there’s another group of long-lived men, japanese-Americans. They have a similar gene to the Laron syndrome group.

Back in Calabria, scientists are trying to work out exactly how much of the longevity is due to genetics and how much to environment. By checking public records going back to the 19th century, researchers have reconstructed the family trees of 202 nonagenarians and centenarians. They (29) _______ that there were genetic factors involved.

(Source: http://www.rwilfe.com/long-ruld-healthy-life-0)

Điền vào số 28