Both of these verbs express the idea of knowing, but they are used in different contexts and are not interchangeable.
Saber is used when referring to facts or learned skills.
¿Tú sabes manejar? - You know how to drive?
Ellos saben qué hora es. - They know what time it is.
Conocer is used to convey familiarity.
Ella los conoce. - She knows them.
The context of the sentence is of familiarity - "Do you know California?" or "Are you familiar with California?" so the correct answer is b. conoces.
Answer:
¿Tú conoces California?
