<human>:  Who was the first to propose the theory of recombination and annihilation?
<bot>: The theory of recombination and annihilation was proposed by the physicist Niels Bohr. In the early 1900s, Bohr proposed that electrons could be emitted from atoms and then reabsorbed into the atom. This process is called recombination. He also proposed that electrons could be emitted from atoms and then annihilated with other electrons, which is called annihilation.