Answer:
The correct formula is the first one.
Explanation:
Copper has two valences I and II, in this example, it's mentioned that copper's valence is I.
Then we have to look in all the formulas for one formula where copper has that valence, and that valence is in formula 1 and 3. Number 4 is discarted that formula is incorrect, that formula doesn't exist.
Number 2 is also discarted because in this formula Cu has a valence of 2.
Number three is discarted because here Bromide has a valence of 2 and that is incorrect, Bromide's valence is 1.
