Why declare static classes as sealed and abstract in C#?

Question

This MSDN article states that static classes should be declared as sealed and abstract. I was under the impression that static classes were already sealed. Why would you als

Answer 1

I think the pertinent bit from that article is:

"Do declare static classes as sealed and abstract, and add a private instance constructor, if your programming language does not have built-in support for static classes."

Remember, the .NET framework supports a lot of different languages.