If crystal growth does not start on its own after the solution in the flask returns to room temperature, identify the best ways to promote this process. a. Add ice cubes to the solution.
b. Scratch the bottom of the flask gently with a stirring rod.
c. Add a bit of solid as a seed crystal.
d. Place the flask on a hot plate to evaporate some solvent.

i think its 100

i hope this !

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.