I find it best when translating to stick as close as possible to the original sentence, not changing word order or getting too idiomatic. DL seems to be pretty literal-minded.
You need a pronoun unless it is a singular family member (is my understanding, no expert here). For example, Le mia figlie (my sisters, plural, needs pronoun) mia figlia (sister, singular, no pronoun). Please someone correct me if I am wrong.
I live in Italy for a good part of the year, and have heard "la tuda domande e comune" often enough to think this is a glitch of the database's option-set.
So, if 'comune' is common, then what is 'commune' (as in Marxist verbiage)?
I see (E) common and (I) normale as synonymous; (I) comune seems too 'common'... lol.