TOEFL Listening: TPO-TOEFL听力TPO - 39Q3AC7K74P53Q51R$

What does the professor imply about the invention of eyeglass? A. Its historical records are more detailed than those of other inventions B. It has little impact on social attitudes toward vision correction C. Its occurrence in different places at approximately the same time is out unusual D. It contributed to a substantial increase in the number of literate people.