Email and instant messaging have had what effect on the corporate grapevine?

These communication channels have dramatically changed the topics of interest communicated through the corporate grapevine.

These communication channels have had no effect on the corporate grapevine.

These communication channels have made it more difficult for the grapevine to operate without the assistance of management.

These communication channels have increased the efficiency and geographic dispersion of grapevine communication.

These communication channels have had all of the given effects.