The correct answer is 'Offers greater speed and is less susceptible to privacy problems'.

• Email provides a certain level of formality instant messaging doesn't, which can either be good or bad. While email isn't usually used for a casual chat or quick questions, it's a good choice when it comes to:
  • Scheduling an interview
  • Contacting a client for the first time
  • Managing disciplinary actions
• Email leaves a "paper" trail you can locate instantly or archive if necessary. However, using an email as a default communication tool might not be an ideal option. Not only is it overly formal and old-fashioned, but it's also quite unproductive.  According to some estimates, an average employee receives 122 emails per day; only 38% of them contain important information.
• Instant messaging: Instant messaging isn't the most suitable way to conduct a formal conversation, but it might be ideal for internal communication among colleagues. Due to the variety of features it offers, instant messaging is excellent for teamwork. It is also reliable, cheaper and boosts effective communication.
• Thus, from above we can conclude that the correct answer is option 4.