最终，工程师们克服了一个又一个难题，港珠澳大桥于2017年7月7日实现了全面贯通。

A.Finally, engineers overcame the difficulties one by one, and the Hong Kong-Zhuhai-Macao Bridge opened on July 7, 2017.

B.Finally, after innumerable difficulties had been overcome, the Hong Kong-Zhuhai-Macao Bridge was fully opened on July 7, 2017.

正确答案：Finally, after innumerable difficulties had been overcome, the Hong Kong-Zhuhai-Macao Bridge was fully opened on July 7, 2017.