Fill in the blanks: $[20$ points$]$

a$.$ When you open file for writing, you can ensure that an existing file is not

truncated by using $\_\_\_\_\_\_\_\_\_,$ which allows fopen to open the file only if it

does not exist.

b$.$ Function $\_\_\_\_\_\_\_$ is normally used to write data to a random$-$access file.

c$.$ Function $\_\_\_\_\_\_\_$ writes a line to a specified file.

d$.$ A group of related characters that conveys meaning is called a$($n$)\_\_\_\_\_\_.$