The correct option is A Improved technology
With rapid improvement in medicine, agriculture and technology, we have been able to not only improve quality of life but also increase the average lifespan. Improvement in medicine has decreased death due to diseases and other medical reasons. Antibiotics and vaccines have reduced the incidence of many diseases and mitigated the adverse effects due to it. Further advances in agriculture and technology have reduced famines and increased the means to mass production of food so as to sustain huge populations. Therefore, we have seen a rapid increase in the human population on this planet.