Question

why is fusion nuclear energy currently not widely used as a source of electricity?
fusion reactions have not yet been achieved.
fusion reactions cannot be controlled.
fusion reactions require very high temperatures and pressure.
fusion reaction energy cannot be converted into electricity.

Explanation:

Fusion reactions need extremely high temperatures and pressures to occur. Currently, it is difficult to maintain such conditions on a large - scale and cost - effective basis for widespread electricity generation. Although fusion reactions have been achieved in experimental settings and energy from fusion can, in theory, be converted to electricity, the high - temperature and pressure requirements remain a major hurdle. Also, while controlling fusion reactions is a challenge, the main immediate obstacle is the high temperature and pressure demands.

Answer:

Fusion reactions require very high temperatures and pressure.