I'm pretty sure the correct answer is D, not B.
"Conoces tu el Valle de Silicio" makes more sense than "Sabes tu el Valle de Silicio". By saying "Conoces tu el Valle de Silicio" you are properly asking in Spanish "Do you know of the Silicone Valley?" or "Do you know about the Silicone Valley?"
So I would go with D, and Spanish is my native language.
