"These are bought at the shopping mall."
Translation:Questi si comprano al centro commerciale.
Yeah I'm a little confused since the English is written in passive voice and as far as I know we haven't covered that. But, maybe comprano is one of those backwards verbs like piachere where the active voice in Italian translates to passive voice in English? I'm pretty confused though, so it is probably not that.
I think Dl is trying to teach the passive but this sentence can be translated much easier using just the past participle....... Questi sono comprati al centro commerciale...which DL accepted. The past participle appears to be used as a noun or as an adjective sometimes.. DL has used it before as in...È morto...He is dead. I have also seen È venduto...It is sold.
si is used in formation of impersonal sentences, sentences where the subject is unspecified eg. si va spesso in quel paese in estate but when si is used and the subject has been specified(as in our sentence) then this is called "si passsivante" which is almost equivalent to the english passive voice eg. compro le riviste al chiosco - i buy newspapers at the kiosk le riviste si comprano al chiosco - newspapers are bought at the kiosk