Context: Unfortunately, requiring two characters to mark the end of a line introduces unnecessary complexity and questions as to how to interpret each character when encountered alone. To simplify matters plain text data streams, including files, on Multics used line feed (LF) alone as a line terminator. Unix and Unix-like systems, and Amiga systems, adopted this convention from Multics. The original Macintosh OS, Apple DOS, and ProDOS, on the other hand, used carriage return (CR) alone as a line terminator; however, since Apple replaced these operating systems with the Unix-based OS X operating system, they now use line feed (LF) as well.

Question: Why is adding two characters at the ned of a line problemsome? 
Answer: introduces unnecessary complexity and questions as to how to interpret each character when encountered alone

Question: What id Multics use to simplify plain text data?
Answer: line feed (LF) alone as a line terminator

Question: Who adopted this practice from Multics?
Answer: Unix and Unix-like systems, and Amiga systems

Question: What used carriage return(CR) alone as a line terminator?
Answer: Macintosh OS, Apple DOS, and ProDOS

Question: When did Apple replace their CR with line feed (LF)?
Answer: since Apple replaced these operating systems with the Unix-based OS X operating system

Question: Why is adding the Unix-based operating system at the end of a line problemsome?
Answer: Unanswerable

Question: What did characters use to simplify plain text data?
Answer: Unanswerable

Question: Who adopted this practice from Apple?
Answer: Unanswerable

Question: What used carriage return(CR) alone as a data stream?
Answer: Unanswerable

Question: When did Amiga stystems replace their CR with line feed (LF)? 
Answer: Unanswerable