Bacteria multiply rapidly by means of binary fission. Binary fission is a type of asexual reproduction in which a single bacterium divides into two identical daughter cells. This process involves DNA replication, followed by the elongation of the cell and the separation of the two identical DNA copies into each of the two daughter cells. This means that bacteria can multiply rapidly and produce a large number of offspring in a short period of time, allowing them to quickly colonize new environments and grow in number. The other options, such as budding, fragmentation, and spore formation, are types of reproduction or growth that occur in some other organisms but not in bacteria.