The description obtained with the command emploi offers the best way to determine which syntax should be used to get the desired results:
> emploi ubv display a small menu
which item? 4
back to the menu (y/n)? y
which item? 7
back to the menu (y/n)? n
The same menu may be displayed with the option -h: ubv -h. A hypertext version is available with NCSA Mosaic: the command name is xhelp and it takes a command name as argument, like in xhelp ubv.