A two-way teleporter can teleport to either a receiver or another two-way teleporter. Likewise, a one-way teleporter can teleport to either a receiver or a two-way teleporter.
Am I right in thinking you want Teleporter (unmarked) to link to Receiver A, and Two-Way Teleporter B to link to Two-Way Teleporter C (in both directions)? If so, just make sure the S Value of (unmarked) and A are the same, and that the S Value of B and C are the same as each other (but different from (unmarked) and A).
Basically, the underlying mechanic is - a teleporter (excluding single-object teleporters, as they simply teleport to themself; but it includes both standard and two-ways) starts looking through the object list, starting from the object after itself (or from Object 0, if Cheapo Mode is active), and wrapping around to the first object if it reaches the end, until it finds an object that is:
> Either a Receiver or a Two-Way Teleporter
> Not fake
> Has the same S value as the sending teleporter
And it sends the lemming to that object. In the event that it finds itself (ie: because there's no receiver / other two-way teleporter in the level with a matching S value), the teleporter is treated as fake.