Marie Curie was born in Poland in 1867. She was the only person who gained two Nobel prizes as that time. She achieved one on physics and one on chemistry. She was born as Marie Sklodowska, the daughter of a chemistry professor. She was the first woman who attended University of Sorbone in Paris. As a poor student, she lived in Paris on only ten cents a day for 3 years. In 1895, she married Pierre Currie, a chemist. They had two daughters: Irene and Eve. Marie managed three lives as a researcher, a wife and a mother. In 1898, Marie discovered radium. Later she developed a concept of radioactivity, which marked the beginning of the atomic age. During World War I, Marie and her daughter completed a new medical tool – the X-ray. Marie died in 1934, only a year before her daughter Irene won the Nobel Prize in chemistry. "In 1898, Marie discovered radium". (paragraph 2) The underlined word means ....

Question

Marie Curie was born in Poland in 1867. She was the only person who gained two Nobel prizes as that time. She achieved one on physics and one on chemistry. She was born as Marie Sklodowska, the daughter of a chemistry professor. She was the first woman who attended University of Sorbone in Paris. As a poor student, she lived in Paris on only ten cents a day for 3 years. In 1895, she married Pierre Currie, a chemist. They had two daughters: Irene and Eve. Marie managed three lives as a researcher, a wife and a mother.

In 1898, Marie discovered radium. Later she developed a concept of radioactivity, which marked the beginning of the atomic age. During World War I, Marie and her daughter completed a new medical tool – the X-ray. Marie died in 1934, only a year before her daughter Irene won the Nobel Prize in chemistry.

"In 1898, Marie discovered radium". (paragraph 2)

The underlined word means ....