Which of the following elements has properties different than the rest? ac co cu sc

Option (a) is the correct answer.

Explanation:

The elements cobalt (Co), copper (Cu), and Scandium (Sc) are all d-block elements and are also known as transition elements. Thus, all these show similar properties as all of them are transition elements.

Whereas Actinium (Ac) is a lanthanide series or f-block element. It shows different properties as compared to transition elements.

Thus, we can conclude that out of the given options, Ac has properties different than the rest.