Because of the costs involved in maintaining high temperatures and pressure, is not yet a practical method for generating electrical energy.

The answer is Fusion

The correct answer is "fusion".

Nuclear fusion requires very high temperatures and pressure. Nuclear fusion occurs naturally in the Sun's core. In the fusion reaction two hydrogen atoms combine to form helium atom. Very high temperatures and pressure is required to overcome the high forces of repulsion between two positively charged protons. The two protons must come together to form helium.

im pretty sure its b