What are carbon-12, carbon-13, and carbon-14?
a. atoms with different number of electrons
b. different elements
c. different isotopes of the same element

C. different isotopes of the same element

Explanation:

Isotopes are the atoms of same element having different number of neutrons. The number of protons is same in all the isotopes which means that all the atoms have same atomic number. Having different number of neutrons, these  atoms have different mass number but same atomic number.

Carbon-12, Carbon-13, and Carbon-14 have same atomic number - 6 but different mass number i.e have different number of neutrons.

Carbon-12 has 6 neutrons, carbon-13 has 7 neutrons and carbon 14 has 8 neutrons. These are different isotopes of the same element.

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