Which statement about fusion reactors is true? a enriched uranium isotopes are used as fuel in fusion reactors. b fuel for fusion reactors can be extracted form ocean water. c fusion reactors are now replacing fission reactors. d fusion reactors produce radioactive waste as spent fuel .

b Fuel for fusion reactors can be extracted from ocean water.  

Explanation:

The fuel is deuterium, which makes up 0.02% of the hydrogen atoms in water. The oceans contain more than a billion cubic kilometres of water, so that's a lot of deuterium.

a is wrong. The fuel for fusion reactors is deuterium.

c is wrong.  There is much research, but there are no large-scale fusion reactors in operation.

d is wrong. Fusion reactors do not produce radioactive waste as spent fuel. Most of the radioactive waste would be the reactor core itself.