In 1978 the who–whom distinction was identified as having "slipped so badly that [it is] almost totally uninformative". According to the OED (2nd edition, 1989), whom is "no longer current in natural colloquial speech". Lasnik and Sobin argue that surviving occurrences of whom are not part of ordinary English grammar, but the result of extra-grammatical rules for producing "prestige" forms."
In Italian, the present could be used for usual actions (e.g. "Chi inviti a cena quando organizzi questi eventi a casa tua?"), for something that is going on right now or in the immediate future (e.g. Chi inviti alla cena di stasera?). I don't feel it could be used for actions happened in the past.
In this exercise the proffered translations from the drop down menus, for "chi inviti" gives the choice of who or whom, and (you)invite. These options offer, in english, no indication as to when this invite is offered, or the gender or otherwise of the person being questioned. To mark any response which uses the past tense as incorrect is, in my view, wrong.