Which of the following commands lists all defined variables and functions within Bash?

The `env` command primarily displays or sets environment variables, not all shell variables or functions.

The `set` command without any options outputs all shell variables, including local variables, environment variables, and shell functions, providing a comprehensive list of what's defined in the current shell session.

The `env -a` option is not a standard or valid option for the `env` command to list all variables and functions; `env` focuses on environment variables.

`echo $ENV` would only print the value of the `ENV` environment variable, which usually points to a script to be sourced, not a list of all variables and functions.