how to populate select in form builder with data from process variable

hi,

i'm facing a problem and i hope to find help here.
i'm trying to populate select in form builder with data from process variable of type
list of options.
i'm able to get the first value via ../API/bpm/activityVariable/{{activityId}}/[variable_name]
but nothing more. besides that, how do i return this variable value via formOutput ?

thanks in advance

gj.