We want to see why electromagnets are more useful in modern technologies.
We will see that the correct option is D:
"By controlling the current, electromagnets can be turned on and off."
An electromagnet is, as the name implies, a magnet that works with a power supply.
Why these are more useful than normal magnets?
Because you have more control over them. By controlling the current, you not only can turn it on and off, but you also could regulate the strength of the magnetic field.
This extra control is what makes the electromagnet a better option than a permanent magnet.
So the correct option is D: "By controlling the current, electromagnets can be turned on and off"
If you want to learn more, you can read:
https://brainly.com/question/1423150
