Answer and Explanation:
The answer is d. leading to write-downs of mortgage-backed securities and fears of a Great Depression-like downward spiral.
The question has to aspects 1) the writing down of mortgage-backed securities and 2) Fears of a great depression-like downward spiral.
The reason for not selecting option a and option b is that both sentences do not have these two aspects in parallel to each other.
Option c has the parallel affect, however, it has the word 'the' twice for the same affect. Idiomatically sounds wrong.
Option e does not have that parallel relationship.
Option d is the right choice since it takes into account the parallel relationship as well as correct idiomatically.