Sentence Correction

Since 1989, after the Berlin Wall had been demolished, one of the most problematic ethnic groups in the reunified Germany, in cultural and economic assimilation terms, were the former East Germans, who have had to acclimate to an entirely different political system.

after the Berlin Wall had been demolished, one of the most problematic ethnic groups in the reunified German, in cultural and economic assimilation terms, were the former East Germans

after the Berlin Wall was demolished, one of the most problematic ethnic groups in the reunified Germany, in cultural terms as well as those of economic assimilation, were the former East Germans

when the Berlin Wall was demolished, one of the reunified Germany's most problematic ethnic groups, in terms of cultural and economic assimilation, was the former East Germans

when the Berlin Wall was demolished, one of the most problematic ethnic groups in the reunified Germany, in terms of cultural and economic assimilation, has been the former East Germans

after the Berlin Wall had been demolished, one of the most problematic ethnic groups in the reunified Germany, in both terms of cultural and economic assimilation, have been the former East Germans

[spoiler]
OA: D[/spoiler]

The problem with D is that it first uses 'has been' for one of the groups- East Germans (definitely singular) and then uses 'who have' in the original sentence. doesn't 'who have' refer to the same one of the groups- East Germans. And isn't East Germans a proper noun?

anantbhatia wrote:Since 1989, after the Berlin Wall had been demolished, one of the most problematic ethnic groups in the reunified Germany, in cultural and economic assimilation terms, were the former East Germans, who have had to acclimate to an entirely different political system.

after the Berlin Wall had been demolished, one of the most problematic ethnic groups in the reunified German, in cultural and economic assimilation terms, were the former East Germans

after the Berlin Wall was demolished, one of the most problematic ethnic groups in the reunified Germany, in cultural terms as well as those of economic assimilation, were the former East Germans

when the Berlin Wall was demolished, one of the reunified Germany's most problematic ethnic groups, in terms of cultural and economic assimilation, was the former East Germans

when the Berlin Wall was demolished, one of the most problematic ethnic groups in the reunified Germany, in terms of cultural and economic assimilation, has been the former East Germans

after the Berlin Wall had been demolished, one of the most problematic ethnic groups in the reunified Germany, in both terms of cultural and economic assimilation, have been the former East Germans

[spoiler]
OA: D[/spoiler]

Answer is D for the following two reasons:

1. One of the + Plural NOUN + Singular verb is correct.
--> This kills A, B, C, and E.
2. The word "since" indicates that it needs present perfect tense.

Answer is D.