Answer:
He had mastered the art of healing wounds. The old General of Japan had full faith in his abilities as a surgeon. He did not believe any other doctor. He was not keeping good health and could require a surgery any time, so Sadao was not sent with the troops abroad.
It's avail, avail means make use of
Difficult—> complex
Think—> realize
Big—> prominent
Make—> manufacture
A. "what he told me before, i have it in my heart."
