—I hear Sam has gone to Qingdao for his holiday.  

—Oh, how nice ! Do you know when he        ?  [ ]

A. left                          

B. was leaving

C. has left                        

D. had left

钢筋应安批进行验收。每批由（）的钢筋组成。

A.同一重量

B.同一炉号

C.同一规格

D.同一牌号