— I'm afraid you can't take photos in the exhibition, sir.

— I'm sorry. I _____ the sign. [ ]

A．can't see

B．haven't seen

C．don't see

D．didn't see

假设一国人口为2000万人，就业人数为900万人，失业人数100万人，那么，该国的劳动力为（）万人。

A.2000

B.1000

C.900

D.800