Which sentence shows that maglev trains create specific challenges?
A
They go up to 600 kilometers per hour
(around 370 miles per hour).
B
Maglev trains are moved by electric
motors located in the guideway.
С
These magnets use less electricity than
conventional electromagnets, but they
must be cooled to temperatures as low
as minus 267 degrees Celsius (minus 450
degrees Fahrenheit).
D
This raises the train off the track a few
centimeters into a "floating" position.

close lines strong magnet less close weaker

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia