The human immunodeficiency virus is the virus that causes AIDS.

When he had a problem due to his own actions, he remembered the phrase 'chickens come home to roost'.

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

Three days ago, I went to Tokyo.

He was anxious about starting a new business, but I encouraged him by saying, 'Even a journey of a thousand miles begins with a single step.'

World War I was a large-scale war that lasted from 1914 to 1918.

He said, 'If you want to shoot a man, first shoot his horse,' and began to solve the smaller problems first.

Zoonosis is a disease that spreads from animals to humans, or vice versa.

In order to solve problems, it is important to listen to the opinions of many people, as the saying goes, 'two heads are better than one'.

He tried to work hard and study at the same time, and in the end, he experienced the lesson of 'He who chases two hares catches neither.'