One day, as I was walking, I found some sandy soil beside the road.
Via half-life equation we have:

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes. By plugging those values in we get:

There is 6.25 grams left of Ra-229 after 12 minutes.
Answer:
Low-cost energy. Although building nuclear power plants has a high initial cost, it’s relatively cheap to produce energy from them and they have low operating costs.
Reliable. One of the biggest benefits of nuclear energy is that it is a reliable power generation source.
Zero carbon emissions. Nuclear power reactors do not produce any carbon emissions.
Promising future energy supply.
D. All of the above. When a wire loop is moved or rotated in a magnetic field, there is a change in magnetic flux which produces emf in wire loop and hence electric current is produced.