phrases

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17. According to a study published by Dr. Myrna Weissman, only one percent of Americans born before 1905 had suffered major depression by the age of seventy-five; of those born since 1955, six percent had become depressed by age twenty-four. (A) only one percent of Americans born before 1905 had suffered major depression by the age of seventy-five; of those born since 1955, six percent had become depressed by age twenty-four
(B) only one percent of Americans born before 1905 suffer major depression by the age of seventy-five; if they are born since 1955, six percent become depressed by age twenty-four
(C) of Americans born before 1905, only one percent of them have suffered major depression by age seventy-five, but six percent of those born since 1955 do by the age of twenty-four
(D) major depression is suffered by the age of seventy-five by only one percent of Americans born before 1905, and by age twenty-four by the six percent born since 1955
(E) Americans born before 1905 suffer major depression by the age of seventy-five only one percent of the time, but six percent of those born since 1955 did so by age twenty-four


A

[acecoolan]

Sophia,

Please refer to this post
https://www.beatthegmat.com/dr-myrna-wei ... 23408.html

-A

[ronniecoleman]

the article was published : past tense from the perspective of the readers

now the article talks about an event occured before it published...

so use of perfect tense justified

1905...<< suffered >> after 1955 << article published..>>

so probably tense use is justified........