How will the right answer fit in terms of support and conclusion?

Only the right answer will match the conclusion you highlight in the passage.

Highlight the main conclusion in the passage, if there is one:

The widespread use of encryption software…will bring the writing of biographical history virtually to and end.

[MAIN CONCLUSION]. [BACKGROUND]. but, [SUPPORT]. [SUPPORT], so [INTERMEDIATE CONCLUSION].

Map the wording of the answers to the wording of the passage:

(A) In the future, most private correspondence…

This matches one of the premises. There’s no support given for this though.

(B) The widespread use of encryption software will cause…

Bingo. This one matches the main conclusion.

(C) Historians will probably not have access…

This isn’t even stated in the passage anywhere.

(D) In the future, biographers’ access…

This maps to the intermediate conclusion at the end. You know that just because it’s at the end doesn’t make it the main conclusion. This info was definitely used to support the conclusion in the first sentence. (Stick a ‘therefore’ in between them to check that if you’re not sure).

(E) Public figures’ private correspondence…

The author didn’t actually say that.

(B) is the correct answer.