There is a new problem________in the popularity of private cars that road conditions need improving.

There is a new problem________in the popularity of private cars that road conditions need improving.

A．involved                              B．to involve

C．involving                              D．being involved

There is a new problem________in the popularity of private cars that road conditions need improving.

1. A.
   involved
2. B.
   to involve
3. C.
   involving
4. D.
   being involved