Select the best definition of a virtual connection or path.

		a. a virtual connection is one where the signal only travels through an unguided medium
		b. a virtual connection is one in which a physical path is shared between two users in a half duplex manner (e.g., push-to-talk radios)
		c. a virtual connection is another term for a physical connection
		d. a virtual connection is one in which the physical path is shared by several users, but without their knowledge that the physical path is being shared