TOEFL Listening: TPO-TOEFL阅读TPO - 61173UXX2NM5PQ68N$

According to paragraph 4, which of the following is true of electron microscopes? A. They do not use light to magnify and resolve objects. B. They can magnify the internal structure of a single atom. C. Their earliest versions were not significantly more powerful than light microscopes. D. They had to be modified extensively for their use in biology research.