Circuit switching today uses either of two technologies
1. Space Division
2. Time Division
In Space Division, the path in the circuit are separated from one another spatially. This technology was originally desiged for use in Analog networks but is currently used in both Analog and Digital Networks.
2. Time division multiplexing (TDM) is a communications process that transmits two or more streaming digital signals over a common channel. In TDM, incoming signals are divided into equal fixed-length time slots. After multiplexing, these signals are transmitted over a shared medium and reassembled into their original format after de-multiplexing. Time slot selection is directly proportional to overall system efficiency.
Time division multiplexing (TDM) is also known as a digital circuit switched.
The advantage of TDM is that it needs no cross-points. Its disadvantage is the TSI(Time Slot Interchange)-is that processing each connection create delays. Each time slot must be stored by RAM, then retrieved and passed on.
other two options are not appropriate according to question so simply discard them.