Question

how are nuclear reactions used to meet the world’s energy needs?
○ both fusion and fission are used to generate electricity, but more fission reactors than fusion reactors are in use.
○ fission reactors are used to generate electricity, but fusion is not yet practical enough to be used.
○ both fusion and fission are used to generate electricity, but more fusion reactors than fission reactors are in use.
○ fusion reactors are used to generate electricity, but fission is not yet practical enough to be used.

Explanation:

To solve this, we analyze nuclear reactions for energy:

• Nuclear fission (splitting atoms, e.g., uranium) is used in reactors to generate electricity, with many fission - based power plants in operation.
• Nuclear fusion (combining light atoms, e.g., hydrogen isotopes) is still in research and development; it's not yet practical for large - scale electricity generation due to extreme conditions needed (high temperature, pressure) to sustain the reaction and build cost - effective reactors.
• Option 1: Fusion isn't widely used for electricity now, so wrong.
• Option 2: Correct. Fission reactors generate electricity, fusion is not practical for use yet.
• Option 3: Fusion reactors are not more common than fission, and fusion isn't widely used, so wrong.
• Option 4: Fission is practical (used in reactors), fusion isn't, so wrong.

Answer:

B. Fission reactors are used to generate electricity, but fusion is not yet practical enough to be used.