Answer : The correct option is, (A) forms colorful compounds.
Explanation :
As we know that nickel (Ni) is transition metal with atomic number 28 and it is belong to the 3-d series in a periodic table.
The electronic configuration of 'Ni' is :
![1s^22s^22p^62s^23p^64s^23d^8](https://img.qammunity.org/2020/formulas/chemistry/middle-school/gpqayptw1fal1houl064c64huat0bcv0id.png)
It is a transition elements that has ability to shows variable oxidation state and due to variable oxidation state they forms colorful compounds.
Hence, the correct option is, (A) forms colorful compounds.