Concept:The phrasal verb "take up" means to accept or begin a position or appointment.
Explanation:The sentence requires a word that combines with "take" to form a correct phrasal verb.
"Take up the appointment" naturally means to accept the appointment.
Option A, "take in", means to deceive or absorb.
Option C, "take on", usually means to accept a challenge.
Option D, "take to", means to develop a liking for something.
Therefore, option B fits best in this context.
Answer:B. up