Demography is a part of social science that studies the structure, evolution, and problems of human population.

Demography is a branch of social science that studies the structure, distribution, and changes in human population.

We played a match on the artificial turf soccer field.

He was drawing a character of a yellow person.

Looking at the population pyramid, you can see that this country is aging.

An old person was playing with his grandchild in the park.

An old person was walking in the park.

The Yi were an ancient tribe in eastern China.

Male and female whales live in the deep parts of the sea.

Suan Ni is a creature from Chinese legends.