TOEFL Listening: TPO-TOEFL听力TPO - G985IWMJ6HH45LF3R$

What did eighteenth-century astronomers have in common with astronomers today? A. They could not explain everything they detected with their instruments. B. They knew the correct distances of objects they could not identify. C. Their instruments were not powerful enough to detect spiral nebulae. D. They argued over the natural brightness of variable stars.