Uninformed about students ’ experience in urban classrooms, critics often condemn schools ’ performance as gauged by an index, such as standardized test scores, that are called objective and can be quantified and overlook less measurable progress, such as that in higher-level reasoning.

A. an index, such as standardized test scores, that are called objective and can be quantified and overlook less measurable progress, such as that

B. an index, such as standardized test scores, that are called objective and can be quantified and overlook less measurable progress, such as what is made

C. an index, such as standardized test scores, that is called objective and can be quantified and overlook less measurable progress, such as what is made

D. a so-called objective index, such as standardized test scores, that can be quantified and overlook less measurable progress, such as what is made

E. a so-called objective index, such as standardized test scores, that is quantified and overlook less measurable progress, such as that



I had chosen D but the correct answer is E based on the fact that "such as that" is less awkward than "such as what is made in".

What bothers me though is that E looked wrong at first glance because of the fact that the verb "to overlook" is not matched with the singular subject "so-called objective index" whereas "to be" (that IS quantified) is.
Could Kaplan have made a mistake in solely focusing on the concluding phrase as the determining factor between C, D and E ?