Sentence Correction

you get a virtual beer for that one.

Cheers!

I know this topic has been done to death but I still have my doubts in the question below

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.
A. 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
B. 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
C. 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
D. 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
E. 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


OA [spoiler][d][/spoiler]


Am i wrong in understanding that "one of the most problematic ethnic groups" is plural.


IMP.
(a) Angelina Jolie is one of those actresses who has international appeal
(b) Angelinaf Jolie is one of those actresses who have international appeal.


Of the above (b) is correct.
This sentence places Angelina Jolie in a category of people who share a trait. Thus it is referring to a group as a whole and takes 'have'. --- The actresses have , not the Actresses has.


Angelina is just one of the many being referred here.