Certain characteristic demographic features of developing countries are -

The correct option is B High fertility, low or rapidly falling mortality rate, rapid population growth and a very young age distribution
Demographic is the study of a population based on age, race, and sex. The socioeconomic characters of a population expressed statistically is called as demographic features. Demographic also include education, profession, income level, marital status etc. The characters of demographic features are population growth, Age structure, birth rate, high fertility etc.

So, the correction option 'High fertility, low or rapidly falling mortality rate, rapid population growth and a very young age distribution'.