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