This definitely took me longer than 2 minutes and almost got me the wrong answer, but one thing you realize is that study was already done. And time frame is past. So you have to use past perfect tense to show what was done in the past.

Study was done - people already suffered...

only A uses the correct verb form.

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

Right Tense..... Correct



(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

Wrong tense ( Suffer )

(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


Wrong tense ( we don't need present participle )


(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

Bloody Passive....Wrong

(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

Wrong Tense

but what the absolute justification for HAD