“Advances in computer technology” is too broad; the author discusses only electronic mail. In addition, the author isn’t trying to show that the right to privacy has been eroded or threatened. Rather, she simply draws attention to certain questions about privacy that are raised by electronic mail.

Although the author does discuss email in the government and private sectors in P2 and P3, the overall purpose of the passage isn’t to compare how email is handled in these sectors. Both sectors are brought up to present examples of questions that are raised regarding privacy of email.

The author mentions telephones and in-person communications at the beginning of the passage, but doesn’t draw out an “extended” analogy in the rest of the passage. She switches subjects to electronic mail and discusses electronic mail in the rest of the passage.

This best captures the primary purpose, which is to tell us about questions surrounding the privacy of electronic mail. The author discusses examples of these questions in P2 and P3 and the limits of certain methods for protecting privacy in P4.

The author doesn’t discuss any reasons that courts haven’t been able to make definitive rulings on the issue of privacy of electronic mail. The author does discuss how one court ruled in P3, and mentions how court have considered interoffice communications in the private sector, but doesn’t get into whether rulings are not definitive and why they’re not definitive.