[求助]请教大家一道题，谢谢

大全885 03-8    Some
of the tenth-century stave churches of Norway are still standing,
demonstrating that with sound design and maintenance, wooden buildings can last
indefinitely.B

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

(B) standing,
demonstrating how wooden buildings, when they have sound design and
maintenance, can last indefinitely

(C) standing; they
demonstrate if a wooden building has sound design and maintenance it can last
indefinitely

(D) standing, and
they demonstrate wooden buildings can last indefinitely when there is sound
design and maintenance（A）