Hi anu1706 and kanigmat011,
Though I am not an expert , I will try to explain my thought process.
For those who walk through the surrounding maze of streets, the dynamics that make Buenos Aires – one of the great immigrant cities of the developing world – comes into focus.1. ) Even I felt "Dynamics" should be singular and not plural. But whenever you encounter a situation where you are confused whether a particular term is singular or plural, always look for consistency in the answer choices. i.e. all references to that particular term must be either singular or plural.
Employ this rule and you will eliminate few choices right away.
(Choices A,B and C in this case)
2.) Idioms play a part here. Idioms such as "Declare", "Consider" and "Make" do not take anything (as, to be etc.).
--> Declare X Y - The Supreme Court declared all fundamental rights unconstitutional. ( does not take "as", "to be" etc. )
--> Consider X Y - I consider myself a good friend of the senator. ( does not take "as", "to be" etc. )
Similarly, "Making
Buenos Aires one of the great immigrant cities" is correct. Hence Eliminate option D which uses "to be".
(A) that make Buenos Aires – one of the great immigrant cities of the developing world – comes into focus -->
make (plural ) and comes (singular) - Wrong(B) that make Buenos Aires, which is one of the great immigrant cities of the developing world, comes into focus -->
make (plural ) and comes (singular) - Wrong(C) which make Buenos Aires one of the great immigrant cities of the developing world comes into focus -->
make (plural ) and comes (singular) - Wrong(D) making Buenos Aires to be one of the great immigrant cities of the developing world come into focus -->
Idiom must be Make X Y and not Make X to be Y - wrong(E) making Buenos Aires one of the great immigrant cities of the developing world come into focus -- >
SV matching and correct idiom - Make X Y - Correct