Is it normal that in September hotels near universities are overcrowded, _____ many parents from a distance nowhere to stay but to sleep on the playground ?

1. A.
   to leave
2. B.
   left
3. C.
   leaving
4. D.
   leave

Is it normal that in September hotels near universities are overcrowded, _____ many parents from a distance nowhere to stay but to sleep on the playground ?

   A. to leave       B. left            C. leaving           D. leave

Is it normal that in September hotels near universities are overcrowded, _____ many parents from a distance nowhere to stay but to sleep on the playground ?

   A. to leave               B. left                 C. leaving              D. leave

Is it normal that in September hotels near universities are overcrowded, _____ many parents from a distance nowhere to stay but to sleep on the playground ?

　 A. to leave 　　　　 B. left 　　　　　 C. leaving 　　　 D. leave

Is it normal that in September hotels near universities are overcrowded, _____ many parents from a distance nowhere to stay but to sleep on the playground ?