The widespread use of encryption software, which makes electronic documents accessible by password only, will bring the writing of biographical history virtually to an end. Public figures' private correspondence and diaries are intended to be confidential when written, but they later become biographers' principal sources. In the future, most such documents are material will be unavailable to historians unless they have the necessary passwords.
What this question is testing
Conclusion
Encryption is going to kill biographical history. Done. Game over for biographers.
Evidence
Biographers depend on private letters and diaries that eventually become public. But in the future, all those juicy documents will be locked behind passwords that historians will never have. No documents, no biographies.
Evaluate
The argument is a domino chain: encryption locks documents, locked documents are inaccessible, inaccessible documents mean no biographies. The first sentence announces the grand conclusion; the rest explains the mechanism. Do not confuse the steps in the chain with the final destination.
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