If a man could fall through a hole that passes through the center of Earth, gravity would cause him to: A. Gain speed until he reached the other end of the tunnel.
B. Stop falling at the center of Earth.
C. Gain speed until he passed the center and then lose speed until he reached the other side.

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.