Which sentence contains an error in pronoun-antecedent agreement?

More than a hundred million e-mails are sent around the world each day, and they are all vulnerable to interception. digital technology has aided communication, but it has also given rise to the possibility of those communications being monitored. according to zimmermann, cryptographers have a duty to encourage the use of encryption and thereby protect the privacy of the individual. —the code book, simon singh what is the purpose of the statistic in this passage? it shows how big the need is for protection. it explains that email is an effective form of communication. it gives new ways to monitor email traffic. it illustrates how popular email has become.