Is an oil pipeline a simplex system, a half-duplex system, a full-duplex system, or none of the above? What about a river or a walkie-talkie-style communication?

Answer:

Oil pipeline - Simplex

River - Simplex

Walkie-talkie-style communication - Half-Duplex

Simplex

The communication is unidirectional, onyl of the devices on the link can transmit.

Half Duplex

The communication is bidirectional, but not at the same time when one device transmit, the other has to recieve, after the transmission complete, then the next one can transmit.

Full Duplex

The communication is bidirectional both the device can transmit and receive at the same time.

Oil Pipeline

It has one source and reciever, the source always sending oil to receiver, so its simplex.

River

River is always flowing in one direction, it cannot flow in the opposit direction it flow, so its simplex

Walkie-talkie-style communication

In this communication only one can speak at time, after that other can start speak. that means it allows communication in both the direction, but not in same time. so it is Half-Duplex