Rehabilitation Techniques | MCQs

Explanation

 The use of "had been doing" in your sentence would indicate that the action of doing the kind of work occurred before another past event.

In this case, "had been doing" implies that the kind of work you were doing happened before the doctor knew you would recover.

This construction suggests a past continuous action that was ongoing up until a specified point in the past, which is why "had been doing" is used in this context.