William the conqueror and his successors did a. introduce common laws, customs, and language c. establish a 12 member jury and court system b. make the central government more efficient d. establish the english parliament with two houses

William the Conqueror and his successors were not able to establish the English Parliament with two houses. However, he was able to do the rest of the choices that's mentioned in the question, especially in making the central government more efficient.