Three key splits can be used to answer this question.
Split #1: Subject-verb agreement.
Split #2: Verb tense.
Split #3: idiomatic construction of ratio of x to y vs ratio of x with y
Option A: Although women’s wages are improving, Department of Labor statistics show that
the ratio of their earnings
with that of men
have been roughly static
since 1960.
Subject 1:
wages verb
are improving, however, this subject verb pair is in the non-underlined portion of the sentence. Subject 2:
[The ratio verb:
have been. There is subject-verb disagreement. The subject is singular, while the verb is plural. We can therefore eliminate option A.
Option B: Although women’s wages are improving, Department of Labor statistics show that
the ratio of their earnings
to those of men
are roughly static
since 1960.
Subject 2:
the ratio Verb:
are. Plural verb are is not appropriate for a singular subject, we can therefore eliminate option B.
Option C: Although women’s wages are improving, Department of Labor statistics show that
the ratio of their earnings
with that of men
have been roughly static
since 1960.
Subject 2:
the ratio Verb:
have been. Plural verb
have been is not appropriate for a singular subject.
Option D: Although women’s wages are improving, Department of Labor statistics show that
the ratio of their earnings
with those of men
is roughly static
since 1960.
Subject 2:
the ratio Verb:
is[/i]. The singular verb [i]is agrees in number with the singular subject
the ratio. Let's keep option D.
Option E: Option D: Although women’s wages are improving, Department of Labor statistics show that
the ratio of their earnings
to those of men
has been roughly static
since 1960.Split #2: verb tense.
The phrase
since 1960 suggests that the verb has to be in the present perfect tense.
The use of simple present verb tense
is is not correct in option D. We can, therefore, eliminate option D. The same verb tense error is present in option B as well, and this can be a ground to eliminate option B.
The right answer is option E. The verb
has been is rightly in the present perfect tense. Options A and C also have the right tense.
Split #3: Idiomatic use of
ratio of x to y vs
ratio of x with y. Ratio of x with y is awkward, and cannot be correct. It does not make sense to say the
ratio of x with y. The correct form should be
ratio of x to y. Based on this, options A and D are incorrect.