_________ March 28, about 20 Chinese cities turned off lights of major buildings for one hour.

1. A.
   At
2. B.
   In
3. C.
   On
4. D.
   Of

_________ March 28, about 20 Chinese cities turned off lights of major buildings for one hour.

_______ March 28，about 20 Chinese cities turned off lights of major buildings for one hour．

A．At          B．In          C．On          D．Of