问题详情

According to the professor, what did a 1920s telescope allow astronomers to dc for the first time？

A．Study the moons of Jupiter

B．Observe gamma-ray bursters

C．Reject the dust theory of nebulae

D．Prove that galaxies are surprisingly small

此题为多项选择题。请帮忙给出正确答案和分析，谢谢！