The first United States Solicitor General, Benjamin H. Bristow, born in 1832 and served in the Grant administration from 1874 to 1876. Earlier in his life, Bristow had served as a lieutenant colonel in the 25th Kentucky Infantry.
A) born in 1832 and served in the Grant administration from 1874 to 1876. Earlier in his life, Bristow had served as a lieutenant colonel in the 25th Kentucky Infantry
B) was born in 1832 and had served in the Grant administration from 1874 to 1876. Earlier in his life, Bristow served as a lieutenant colonel
C) born in 1832 and appointee in the Grant administration from 1874 to 1875. Earlier in his life, Bristow served as a lieutenant colonel in the 25th Kentucky Infantry
D) was born in 1832 and served in the Grand administration from 1874 to 1876. Earlier in his life, Bristow had served as a lieutenant colonel in the 25th Kentucky Infantry
E) was born in 1832 and served in the Grand administration from 1874 to 1876. Earlier in his life, Bristow served as a lieutenant colonel in the 25th Kentucky Infantry
OA is E.
But shouldn't the answer be "D" as "had served" in the past perfect tense in D suits the sentence better than just "served" in E (given the different times).
Source: platinum.gmat.com (somebody recommended this site in one of these forums)