Motives or reasons for changing careers vary widely, but many people move because they feel stale or ________a grinding or dull routine.
句意：改变职业的动机和原因有很多，但很多人换工作只是因为他们觉得这份工作失去了新鲜感或对感到厌烦枯燥乏味的日常感到厌烦。be bound to被束缚于。be fed up with厌倦。be filled with充满。be accustomed to习惯于。因此，本题的正确答案为 B。