SOURCE : MGMAT CAT 2
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
The explanation for this question in the MGMAT mainly relies on the correct verb 'has been' since this is found only in D and matches with the 'Since 1989'
I would like to clarify about additional errors in this SC ...
1) After v/s When - Can either one be used ? I undesrtand that 'When' refers specifically to the year 1989 when the event happened. Can 'after' be used ??... If yes, would it refer to the complete phrase 'since 1989'
2) 'In X & Y terms' in option A - Is this correct usage ? I've normally come across 'In terms of X & Y'- as stated in D
Kindly clarify. Thanks