A.
An informal invitation letter can be written either in the first person or in the third person.
B.
Contents of an invitation letter should always include the purpose of the invitation, the place and the time of the .
C.
The tone of a formal invitation letter tends to be oral, conversational, and friendly.
D.
In an invitation letter, it must be avoided to use the abbreviation form such as “I’m”, “I’ve”, “We’re”, “You’re”, etc..