问题补充：
The airport next year will help promote tourism in this area.
A. having been completed
B. completed
C. being completed
D. to be completed
答案：
A. having been completed
B. completed
C. being completed
(答案→)D. to be completed
解析：句意为：明年即将建成的机场将有助于促进这个地区旅游业的发展。非谓语动词作定语，the airport与complete之间为被动关系，由next year可知为将来，故应为to be done结构。having been done 通常不用于定语；completed 表示完成被动，即已经建成；being done 表示正在进行的被动，即正在建造，与next year不符。
