Hypothesis 2 (Particle size): If you
the particle size of a reactant, then the reaction rate
will increase because of the reactant's surface area is exposed allowing more particles to make
contact with each other

beta decay is the answer

you did not give any options thus this is the best answer i can give to you with this little information you have given

> they are both natural and not man made

> they can be tracked and predicted by the right tools

-love shrooms