This offer shall remain _______ until 10 o'clock, May 5, Beijing

This offer shall remain _______ until 10 o'clock, May 5, Beijing time.
A、effective
B、effectual
C、open
D、opening
【正确答案】：C
【题目解析】：句意：本报盘有效期到北京时间5月5日10点。