Which of the following commands is used to change options and positional parameters for a running Bash?

'history' displays or manipulates the command history list and has no ability to change shell options or positional parameters.

The 'set' builtin command is used in Bash to enable or disable shell options (e.g., 'set -e', 'set -x') and to assign positional parameters. It directly controls the behavior of the currently running Bash instance without requiring an external utility.

'bashconf' is not a real Bash builtin or standard Linux command.

'setsh' is not a real Bash builtin or standard Linux command.

'envsetup' is not a standard Bash builtin; it is sometimes a project-specific script in certain SDKs but has no role in changing Bash options.