Answer: B - Cr(NO3)2
Explanation: The +2 on Chromium and the -1 on NO3 indicates the charge. And in order to balance out the charge, you will sometimes need to add more of a substance.
In this case, Cr has a +2 charge and NO3 has a -1 charge. To balance, the total charge needs to equal 0. So, you add another NO3 to make two -1 charges, which will cancel out the +2 charge on Cr.
