Which best describes fusion nuclear reactors? they use rods containing uranium for fuel. they are currently used for electricity in several highly populated countries. they are used in some naval vessels, such as submarines. they have been successful, but they are very expensive to operate.

A fusion reactor is a facility in which nuclear fusion reactions take place in a fuel formed by hydrogen isotopes (deuterium and tritium), releasing energy in the form of heat, and then transforming it into electrical energy.

At the moment there is no commercial fusion reactor that allows to obtain electrical energy, although there are experimental research facilities where fusion reactions are studied, as well as the technology that will be used in the future.

In other words:

All commercial nuclear reactors currently in use work with nucler fission (separation of the components of the atom nucleous), not nuclear fusion (joining two light nucleous to form a heavier nucleous). And this is because, although experimental reactors have already shown us that nuclear fusion works, it is such a complex process that has not been yet found a way to get the fusion reaction to behave in a stable way for a long time and it is expensive as well.

continuous conducting path for current, power supply

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me