In the vi editor, which of the following commands will copy the current line into the vi buffer?

`c` (change) is a command to change characters, requiring a motion command, and puts `vi` into insert mode after deleting.

`cc` (change line) cuts the current line and immediately puts `vi` into insert mode, deleting the line's content rather than just copying it.

`1c` is not a standard `vi` command for copying a line; it would initiate a change operation on one character.

In `vi`'s normal mode, the `yy` command (yank current line) copies the entire current line into the unnamed buffer. This allows the line to be pasted elsewhere using the `p` or `P` command.

`1y` is not the standard `vi` command for yanking the current line; `yy` is the correct two-character command for this action.