The actual sentence -
Black officers
at the executive rank of general or admiral, of whom there are over seventy in the armed services, have not
, until recently, been present in comparable numbers, either
in amount or
proportion, among high executives in major corporations.
can be simply reduced to -
Black officers have not been present in comparable numbers,either in amount or proportion, among high executives in major corporations.Note that the above sentence ruins the parallelism of
Either X OR Y We can eliminate
(A). Choices
C and D imply that
Black officers have not been matched by Blacks ( or something of Blacks) ... - This makes no sense.
Choice
(B) says -
Black officers have not been present in comparable numbers, either numerically or proportionally, among high executives. This sentence is grammatically correct. The adverbs numerically and proportionally modify the verb "present"
But, look at the meaning.
The phrase "present in comparable numbers" clearly imply the numerical presence. It's incorrect to say "Present in comparable numbers, numerically or proportionally"
Choice (C) fixes the above issue and has no grammatical issue as well.
IMO
C