The school chime rang out, 'keen-korn-karn-korn.'

The center of this plate is sunken.

It is important to learn about the prevention and treatment of the human immunodeficiency virus.

The human immunodeficiency virus destroys the immune system, making the body unable to fight disease.

He is an expert in primatology and is engaged in the study of gorilla behavior.

Cytogenetics is a science that studies the structure and function of chromosomes and genes.

He is an expert in nuclear physics.

He is an expert in fluid mechanics.

My father is an expert in otolaryngology.

He is immersed in the research of deep learning.