The letter writer's initials followed by a colon or slash and the typist's initials constitute the ____.

A) identification line
B) subject line
C) signature block
D) notations
E) closing

Identification Line

A line at the bottom of a letter containing the letter writer’s initials and the typist’s initials.

Typist's Initials

The initials used by a typist as a form of identifying or signing off on documents they have prepared or worked on.