In Beijing, although there is a good public transport system, ________ private car is still becoming ________ popular means of transportation．

1. A.
   不填; the
2. B.
   the; a
3. C.
   the; the
4. D.
   a; 不填

In Beijing ,although there is a good public transport system,         private car is still becoming         popular means of transportation.

A．不填;the   B．the ;a       C．the ;the     D．a(chǎn);不填