[quote="synecdoche"]Each year companies in United States could save as much as $58 billion
annually by preventing illness among employees and gain as much as $200 billion through improving performance of workers if they simply provided offices with cleaner air.
(A) annually by preventing illness among employees and gain as much as $200 billion through improving performance of workers if they simply provided
(B) annually if they prevented employee illness and gain as much as $200 billion through worker performance improved by simply providing
(C) annually in employee illness prevention and gain as much as $200 billion through worker performance improved by simply providing
(D) in employee illness prevention and gain as much as $200 billion through improving performance of workers if they simply provided
(E) by preventing illness among employees and gain as much as $200 billion through improved worker performance if they simply provided
regarding choice d
"employee illness prevention" is not idiomatic.
"prevention" is general action but not the action done by "companies". in choice E, "by preventing" refers to the subject "companies". this means, "companies" do "preventing". agent of preventing is clear and logical.
"main clause+by doing" is good pattern in which "by doing" refers to the subject of the main clause.
these are 2 errors of choice D.
regarding choice e
"improved worker performance" is complex noun. in this kind of long noun phrase, the first "improved" can modify the second noun "worker" or "performance". we can dislike the fact that "improved" modifies " performance" when it is far from "performance" but this modification is correct.
compare "improved worker performance" with "employee illness prevention". both a long noun phrase but one of them is wrong. we can not always make long noun phrase from idiomatice noun+preposition+noun
"prevention of employee illness" is correct.
if we see 2 premodifiers before a noun, the meaning is the first modifier modifies the second modifier+noun. this is normal meaning. but the other meaning, in which the first modifier modifies the second modifier is accepted.