Joe has finished his frist-aid course. He proves extremely helpful as a rescue worker

A. Although Joe proves extremely helpful as a rescue worker, he hasn’t finished his first-aid course.

B. Without finishing his first-air course, Joe proves extremely helpful as a rescue worker.

C. However helpful Joe proves as a rescue worker, he hasn’t finished his first-aid course.

D. Having finished his first-aid course, Joe proves extremely helpful as a rescue worker.