Current rules regarding investment of state employee pension funds req

Current rules regarding investment of state employee pension funds require money managers either to sell at stock in companies that market tobacco products by the end of the year or that they file a timetable for doing so within the next six months.

A. that they file
B. file
C. be filing
D. they should file
E. to file

If we cut down the fluff the sentence looks like this: "Current rules require mangers either to sell or [answer choice] a timetable within the next six months".
In order to maintain parallelism we need to find an answer that is parallel to "either to sell or". Thus, we need an infinitive, which we find in "to file" (answer choice E).

Therefore, E) is the correct answer.