[JEM]

Let's take this step-by-step. A and D are out because the number of bankrupt citizens could not jump "at" some number.

Both forms "declaring themselves" and "who declared themselves" are acceptable; there is only a nominal difference with regard to wordiness that goes in favor of the former.

This brings us to choose between the "has jumped" and "jumped". The correct choice is "jumped", i.e. the past tense becase we are pegging a particular event within the larger historical context of the year 1997.

Now, what about E?

This is a borderline case and I'm not sure of the official rule. Bobotalk may have a better answer, but to a native speaker's ear, E just doesn't sound right.

JEM