The queation requires a proper parallel list: had overcome - sharpened - developed
By the time they completed their journey, the young explorers had overcome their fears, sharpened their survival skills, and had developed a healthy respect for nature’s potential destructiveness.
A. skills, and had developed a healthy respect
By the time they completed their journey, the young explorers
had overcome their fears,
sharpened their survival skills, and
had developed a healthy respect for nature’s potential destructiveness.
B. skills, and developed a healthy respect
By the time they completed their journey, the young explorers
had overcome their fears,
sharpened their survival skills, and
developed a healthy respect for nature’s potential destructiveness.
C. skills and a healthy respect developed
By the time they completed their journey, the young explorers
had overcome their fears,
sharpened their survival skills and
a healthy respect developed a healthy respect for nature’s potential destructiveness.
D. skills, developing a healthy respect
By the time they completed their journey, the young explorers
had overcome their fears,
sharpened their survival skills,
developing a healthy respect for nature’s potential destructiveness.
E. skills, all the while developing a healthy respect
By the time they completed their journey, the young explorers
had overcome their fears,
sharpened their survival skills,
all the while developing a healthy respect for nature’s potential destructiveness.