Help with knowledge check 5.

I have trouble with knowledge check 5.4
Question is

What should be appended to the command in order to affect every namespace with kubectl?

A. This cannot be done
B. --every-object
C. --all-namespaces
D. --all

For my understanding, You can get/describe all namespace's objects with --all-namespaces.
But this won't do any affect to those objects.
Besides, there's no --all and --every-object in kubectl option.
So I chose A - this cannot be done .

But turned out I was wrong.
I tried every option from A to D.
The system always kept showing I have wrong answer.

Please help me with this.
If this is a system bug, please fix this.