At the school sports festival, we did a three-legged race.

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

He is feeling solitude.

The human immunodeficiency virus destroys the immune system, causing the body to lose its ability to fight disease.

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

I started learning new things to broaden my horizons.

This basin was used in ancient washrooms.

I am majoring in auditory phonetics at university.

Linear programming is a part of operations research and is used to find the optimal solution.

I can't find my Allen key.