Giulietta: «Quale devo dare?»
a) Romeo: «Dà questa».
b) Romeo: «Da' questa».
Which one is grammatical, a) or b)?
As far as I can tell in "Da' questa" "Da'" is different from "Dà" because it is the contracted form of "Dai". Am I right?
Giulietta: «Quale devo dare?»
a) Romeo: «Dà questa».
b) Romeo: «Da' questa».
Which one is grammatical, a) or b)?
As far as I can tell in "Da' questa" "Da'" is different from "Dà" because it is the contracted form of "Dai". Am I right?
Yes, you are right. With clearer subjects:
“Giulietta dà questa”
“[Giulietta,] da' questa!”
The second form is correct.
To disambiguate, since “[Giulietta] dà questa a lui” can be a valid sentence with a different meaning and we might not have the context of the conversation, and since apostrophes and accents are (sadly) often confused, using an exclamation mark for the imperative modes might help.
Da' is the short form for dai, and it is used only in Tuscan, or literary.
Dai is the second singular person for the modo indicativo, tempo presente and the modo imperativo (or jussive mood); dà is the third singular person for the modo indicativo, tempo presente. The accent is required to avoid confusion with da, the preposition.