【正确答案】 E

【答案解析】Parallelism; Grammatical construction
The sentence describes a proposal to allow law-enforcement agencies to track people who have not been charged with a crime but are under investigation. However, the description of the group is flawed, in that the two defining properties—not having been charged; being under investigation—are not expressed in a parallel form: the verb have been charged lacks a grammatically correct subject.
A The adjectival phrase under criminal investigation, modifying people, is nonparallel to have not yet been charged; the latter is a mere sentence fragment.
B The required parallelism is lacking here. The word but introduces a sentence fragment.
C The required parallelism is lacking here: we have an adjectival phrase, and the coordinate conjunction but introducing what appears to be an independent clause. It is unclear what the antecedent of the pronoun they is.
D The required parallelism is lacking here: we have a relative clause, followed by the coordinate conjunction but introducing what appears to be an independent clause. It is structurally unclear what the antecedent of the pronoun they is.
E Correct. The relative pronoun who has people as its antecedent and introduces a complex relative clause containing two parallel verbal phrases correctly coordinated with the conjunction but.
The correct answer is E.