The time has come ______ we can make extensive use of nuclear energy．

The time has come ______ we can make extensive use of nuclear energy．

       A．when              B．which     C．since            D．while

The time has come ______ we can make extensive use of nuclear energy．

A．when         B．which               C．since            D．while

The time has come ______ we can make extensive use of nuclear energy．

 The time has come ______ we can make extensive use of nuclear energy．

       A．when          B．which               C．since               D．while

The time has come ______ we can make extensive use of nuclear energy．

1. A.
   when
2. B.
   which
3. C.
   since
4. D.
   while