Which part of an atom participates in the reaction shown below?
u235 + n → xe134 + sr100 + 2n
a) nuclei
b) protons
c) valence electrons
d) inner shell electrons

Option (A) is the correct answer.

Explanation:

A reaction in which nucleus of an atom and a subatomic particle like proton or neutron collide or when any two nuclei combine together then it results in the formation of a new nucleus that is different from its parent nuclei.

For example,

Here, nucleus of Uranium collides with a neutron resulting in formation of a Xenon and Strontium nucleus along with two neutrons.

Therefore, we can conclude that nuclei of an atom participates in the given  reaction.

it has to be b, about 97 percent.