What is a best practice for adding these changes?

A change set has already been uploaded but changes need to be made to its contents.

What is a best practice for adding these changes?
A . Edit existing change set, add needed changes, upload again.
B. Delete existing change set, add changes to new change set, upload change set
C. clone the change set, add needed change set and upload again.
D. Manually make changes in change set destination org.

Answer: C