The answer is Circuit Switching
The correct answer is A. The water at this conditions is in the solid phase. This can be verified by using a phase diagram. A phase diagram is a figure which shows the phases of a certain substance at a specific temperature and pressure.
Answer: 50%
Explanation: efficiency=power input/power output ×100
Eff.=300/600 ×100
Eff=½×100
Eff=50%