He had always had a good opinion of himself, but after the publication of his best-selling novel he became unbearably______.

【正确答案】 C

【答案解析】解析：根据句意此处应为由于小说畅销，而更进一步的骄傲了，应填贬义的骄傲。conceited“自负的，自大的”，最符合题意；cordial“热忱的，兴奋的”；proud“自豪的，得意的”；exaggerated“夸大的，夸张的”。故选C。