for the fact that he was working abroad, he would have helped with the project.

Đáp án B
Giải thích: If it hadn’t been for the fact that + mệnh đề: nếu không có sự thật là …
Dịch nghĩa: Nếu không có sự thật là anh ấy đang làm việc ở nước ngoài, anh ấy đã giúp dự án.

_________ for the fact that he was working abroad, he would have helped with the project.