Task: Paraphrasing
Input (English): Question: What type of particle collides with an atom of u-235 during the basic nuclear fission process? 
Answer: a neutron. 
Sentence: A neutron collides with an atom of u-235 during the basic nuclear fission process.
Output (English): The particle type that collides with a u-235 atom in the process of nuclear fission is a neutron.