The sun's energy source is__________
A. Intense radio waves emitted by sunspots and flares
B. The flow of solar particles thrown by the solar wind
C. Thermal energy generated by the decay of radioactive elements
D. Nuclear fusion reactions of internal substances
Answer:D
The sun's energy source is__________
A. Intense radio waves emitted by sunspots and flares B. The flow of solar particles thrown by the solar wind C. Thermal energy generated by the decay of radioactive elements D. Nuclear fusion reactions of internal substances