Which one of the following is the correct answer to the question?

Although no money changes hands, producers and consumers of Twitter:

can use Twitter for research.

can use Twitter to decide between the opportunity costs of competing goods.

can use Twitter as an economic transaction cost.

can use Twitter for accessing information and feedback.

can use Twitter as an economic externality.

can use Twitter to share information.

can use the information available on Twitter to generate other economic benefits.