POE,
"In what is the third such study of common sunscreen ingredients," This is a modifier. Always in order for the sentence to convey the correct meaning, what follows the modifier must be the doer of the action/ Subject.
Eg: Using the latest technology, the mechanical problem was identified quickly.
The above sentence is incorrect. What follows the modifier " using the latest technology," must be the person using the latest technology.
The correct sentence would read as - Using the latest technology, the engineer identified the mechanical problem quickly.
In such sentences always ask the question "who?"
In what is the third such study of common sunscreen ingredients,
(who conducted the study?) researchers have established...
B)
it has been established by researchers that these chemicals are absorbed into the bloodstream at concentrations far more than the Food and Drug Administration’s safety threshold.
D)
it has been established by researchers that they are absorbed into the bloodstream at far greater concentrations than those of the Food and Drug Administration’s safety threshold.
B and D do not have researchers immediately after the modifier. Eliminate B and D.
C) researchers have established that
they are absorbed into the bloodstream at far more concentrations than the Food and Drug Administration’s safety threshold.
"they" - pronoun error as they has 2 antecedents - researchers and sunscreen ingredients - they cannot refer to the closest antecedent researchers - researchers have established that researchers are absorbed... Eliminate C
A vs E
A) researchers have established that these chemicals are absorbed into the bloodstream at concentrations far
greater than the Food and Drug Administration’s safety threshold.
E) researchers have established that these chemicals are absorbed into the bloodstream at concentrations far
more than that of the Food and Drug Administration’s safety threshold.
since these chemicals can be measured
greater than is the appropriate usage. Eliminate E.
IMO, answer A.