Explanation:
Efficiency is defined as the ratio between the useful output over the total amount consumed. 
The fan does 500W of useful work while wasting 300 W. The total power consumption is 800 W (500 + 300).
Answer:
C. Waves transfer energy, but not matter.
Explanation: hope this helps :)
I’m not too sure but I think it’s 8,91 m/s2
Internal energy cannot be transferred whereas, thermal energy is the energy due to temperature difference