What is unique about a data file's read position and where is it when a file is open for read access?

A$.$ It indicates where the next character position will be written to and as data is written, it moves further into the data file. It begins at the first character position in a data file when opened for read access

B$.$ It indicates where the next character position will be read from and as data is read, it moves further into the data file. It begins at the first character position in a data file when opened for read access.

C$.$ It indicates where the last character position was read from and moves back through the data file as data is read. It begins at the character position the user indicates when opening the file.

D$.$ It indicates where the middle character position of the file is located. It moves wherever the user indicates when randomly accessing the data file. It begins at the last character position in a data file when opened for read access.