フリー問題

問題文

A report has to leave as an encrypted portable document, and the administrator is reading the table that ties each of the four security levels to an encryption scheme with a key length, to a version of the portable document format, and to a version of the reader. What does that table say about the key lengths and about the column of reader versions?

選択肢

1. Two of the levels are given one key length between them, so the length holds steady where the scheme changes, and the column for the reader names a letter at the topmost level in place of a number.
2. The four levels are given four different lengths of their own, so the length moves up where the scheme changes, and the column for the reader names a letter at the topmost level in place of a number.
3. Two of the levels are given one key length between them, so the length holds steady where the scheme changes, and the column for the reader names a number at the topmost level, as rows further down do.
4. The four levels are given four different lengths of their own, so the length moves up where the scheme changes, and the column for the reader names a number at the topmost level, as rows further down do.