The state has proposed new rules that would set minimum staffing levels for nurses, rules intended to ensure that at least one nurse is assigned for every four patients put through triage in a hospital emergency room.

A.rules intended to ensure that at least one nurse is assigned for every four patients put through triage in a hospital emergency room.
B.rules with the intent of ensuring one nurse at least to be assigned for every four patients to be put through triage in a hospital emergency room.
C.rules intending to ensure at least one nurse is assigned for every four patients in a hospital emergency room put through triage.
D.with the intent of ensuring that at least one nurse should be assigned for every four patients in a hospital emergency room that are put through triage.
E.and this is intended to ensure one nurse at least to be assigned for every four patients put through triage in a hospital emergency room.

Choice A looks pretty good, with no obvious issues. So maybe the task here is to see if there are obvious issues that would indicate the elimination of all the other answer choices. So without discussing every issue in each choice, there are many, I am just going to see if all them them have issues.

B. For one thing, rules don't have intent. People who make rules have intent. So this is already looking sketchy because it includes the phrase "rules with the intent". Next, rather than saying that at least one nurse will be assigned, this choice discusses "ensuring one nurse at least to be assigned", which seems to convey that one nurse will at least be assigned to four patients, rather than at least one nurse will be assigned.

C. Once again, rules are intending something. Then at the end the modifier put through triage is placed in such a way as to incorrectly modify hospital emergency room.

D. This version of the underlined portion seems to incorrectly modify nurses, and then the use of the word should makes the modifier itself nonsensical.

E. It is not clear what this refers to. Also, the structure is awkward and creates a somewhat nonsensical statement. What does ensure one nurse at least to be assigned even mean?

So this is a typical GMAT sentence correction in which the incorrect choices have multiple issues and the correct one is clearer and basically grammatically correct.

There are issues in all the other choices. So choose the only one that really makes any sense, A.