Given the question: Li Shizhen was born in 1918 in Hubei province. His father was a doctor. He learned a lot about medical herbs from his father and read many medical books. At the age of 23 he became a doctor. He often treated poor people's illness, so many peasants and fishermen made friends with him. The year he was 35 Li shizhen began to write the COMPENDIUM OF MATERIA MEDICA. He walked all over famous mountains which grew medical plants to learn their shapes. The conditions in which they grew and collected all sorts of specimens . He spent 27 years in writing this book. The COMPENDIUM OF MATERIA MEDICA with over 1,000,000 words, describe 1,800 kinds of medical plants. When the work had just been ready for printing and publishing , Lishizhen passed away. The COMPENDIUM OF MATERIA MEDICA introduces not only medical herbs growing in China but also many foreign medicines. After its publication the books reached foreign countries. It was translated into English, French, German, Japanese and Russian and became an important piece of _ in international medical research. The word "literature" in the article means _ . A) work of different science B) letters from foreign countries C) hope for the better future D) books on special subject
The answer is:
D