Some of the tenth-century stave churches of Norway are still

Hey Guys,

I see there was another thread on this, but there are threads on just about everything. It's still worth discussing!

Some of the tenth-century stave churches of Norway are still standing, demonstrating that with sound design and maintenance, wooden buildings can last indefinitely.

(A) standing, demonstrating that with sound design and maintenance, wooden buildings can last indefinitely
Answer

(B) standing, demonstrating how wooden buildings, when they have sound design and maintenance, can last indefinitely
PROBLEM: "how wooden buildings can last" would imply that the fact that the churches are standing actually shows IN WHAT WAY the buildings can last. But it's merely demonstrating the fact THAT the buildings are still standing. It's also very ugly to interrupt the "wooden buildings can last.." phrase with a relative modifier on buildings (though I wouldn't argue it's necessarily wrong).

(C) standing; they demonstrate if a wooden building has sound design and maintenance it can last indefinitely
PROBLEM: You can't "demonstrate if" something. The semicolon is fine.

(D) standing, and they demonstrate wooden buildings can last indefinitely when there is sound design and maintenance
PROBLEM: No need for the comma before "and". You can't "demonstrate [a physical thing]". You need some weird inbetween. Also unclear to say "there is sound design and maintenance". We'd prefer to describe how the buildings have sound design and maintenance.

(E) standing, and they demonstrate how a wooden building can last indefinitely when it has sound design and maintenance
PROBLEM: Comma before "and" again. "How" issue again.

Hope that helps!

-tommy