Why are songs with multiple beats so catchy? Like in FNF?

The combining of light nuclei is called blank. blank as in not actually blank. you know what im tryin to say.

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.

Need only answer if you think you know it