As soon as James started working, he realized that his decision had not been a good one.

A. Just before James took up his new post, he realized that he was not suited for it.

B. No sooner had James begun his new job than he knew his decision was wrong.

C. Had James not begun his new job, he would have gone looking for a better one.

D. Since James did not like his new job, he began looking for a better one.