There is a relationship between the three measurable parts of an electrical circuit, which are A
current, voltage and resistance.
B
electron, proton and neutron.
С
light bulb, battery and plug.
D
series, simple and parallel.

it's c (engineer's do their work with mechanical stuff not on any living being)

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.