Answer: The correct answer for the fill in the blank is Asexually.
Asexually reproducing organisms have rapid rate of reproduction as only a single parent is involved in this. Also, there is no formation and fusion of gametes in this mode of reproduction.
They produce larger number of offsprings through rapid rate of reproduction. By doing so they have larger chances of survival.
For instance, if a part of bacterial species population is wiped out through viral infection, bacteria can compensate this loss by the rapid rate of reproduction. This increases their chances of survival.