________ global energy safety, all the countries have been called on to take joint efforts ．

1. A.
   Having ensured
2. B.
   Ensuring
3. C.
   To ensure
4. D.
   To have ensured

________ global energy safety, all the countries have been called on to take joint efforts ．

       A．Having ensured             B．Ensuring               

C．To ensure               D．To have ensured