Circle the letter A, B, C, or D to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following questions.For a decade, Barzilai has studied centena

Circle the letter A, B, C, or D  to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following questions.

For a decade, Barzilai has studied centenarians, looking for genes that contribute to longervity.