Li Ping works hard at his lessons , he didn’t pass the exams last time , ________．

1. A.
   though
2. B.
   yet
3. C.
   however
4. D.
   although

Li Ping works hard at his lessons, he didn’t pass the exams last time, ______.

　 A. though　　　　　　 B. yet　　　　　　 C. however　　　　 D. although