Which explanation BEST describes what happened to chocolate bar A? A. Heat was transferred to the chocolate bar by convection causing it to melt.
B.
Heat was transferred to the chocolate bar by radiation causing it to melt.
C
Heat was transferred to the chocolate bar by condensation causing it to meit
D.
Heat was transferred to the chocolate bar by evaporation causing it to melt.

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.