—Bob has gone to California, I hear.

—Oh, I wonder when he ________.

A．has left 

B．was leaving

C．left 

D．leaves

---Bob has gone to California, I hear.

---Oh, I wonder when he ______.

  A. has left         B. leaves           C. left                 D. was leaving

—Oh, I wonder when he ________.

A．has left

B．leaves

C．left

D．was leaving

—Bob has gone to California, I hear.

—Oh, I wonder when he ________.

A．has left

B．leaves

C．left

D．was leaving

—Bob has gone to California, I hear.

—Oh, I wonder when he　　

　　  A. has left　　　　  B. was leaving　　    C. left　　    D. leaves