01 At which stage of demographic transition does a population-explosion-like condition occur?
Answer and explanation
Correct answer: B. जब मृत्यु दर घट जाए, पर जन्म दर लंबे समय तक ऊँची रहे
Explanation: Direct answer: B is correct. In the demographic transition, a population-explosion-like condition occurs when mortality falls substantially but fertility and the birth rate remain high for some time. Improvements in food supply, sanitation, medicine and public health can reduce deaths, especially infant deaths, before families change their reproductive behaviour. Births therefore continue at a high level while deaths become fewer, creating a large positive natural increase. A describes a later low-growth stage, when both rates are low. C would produce natural decrease rather than rapid growth. D concerns migration and does not define the demographic-transition stage. B is correct because the gap between a high birth rate and a falling death rate creates rapid population growth. Memory cue: first deaths fall, then births fall; the gap between them produces the surge.