C. Convection is the transfer of energy by the motion of a fluid. Fluids are by definition substances in which particles are able to flow. Hence the answer is c
<span>They are used to measure and map effluent and pollution discharges from factories and sewerage plants, and the movement of sand around harbours, rivers and bays. Radioactive materials used for such purposes have short half-lives and decay to background levels within days.</span>
Answer:
B is the answer. Correct me if I'm wrong
This assumes that the wave has velocity c (is light).
