单选题 The objective of this popular consultation is to determine,______, the final political status of the region, whether to remain of the country as a special district, or to part from it.

A、 once upon a time
B、 once and again
C、 all at once
D、 once and for all

【正确答案】 D

【答案解析】解析：本题考查词组。once upon a time“从前”；once and again“一而再，屡次”；allat once“一下子”；once and for all“果断地，坚决地，永远地”。根据题意，此处应填onceand for all，表示“坚决地”。故答案为D。