Answer: it is a datasheet because data is like a a place to keep things in and you can organise that in many different way's
The answer to you question is C
Emails are formal
Online chats are private and friendly
Emails are used for business
Online chats are for friends
To put it simple, an Address Book is basically where you can store peoples names, addresses and most importantly emails so you can easily contact them. Its pretty much like your contacts on your phone.
