Collision Theory states that in order for particles to react, there has to be a collision that meets 2 criteria: a. Sufficient or
b. Must collide in proper (this means the molecular collision must have the right orientation in 3-D space)

answer; i believe the correct answer is (solid gold);

the right answer is c i just did the question.

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.