He was working abroad, so he couldn’t willingly help us with the project

A. If he hadn’t worked abroad, he would willingly have helped with us the project.

B. If it hadn’t been for the fact that he was working abroad, he would willingly have helped us with the project.

C. Hadn’t he been working abroad, he would willingly have helped us with the project.

D. Without working abroad, he could willingly help us with the project.