How do you change a foreground process into a background process ?

[A] The simplest way to start a background process is to add an ampersand (&) at the end of the command

[B] The simplest way to start a background process is to add an nice command at the beginning of the foreground process command

[C] The simplest way to start a background process is to add an ampersand (&) at the beginning of the foreground process command

[D] The simplest way to start a background process is to add fg command at the beginning of the foreground process command