A-A+
The passage implies that Leavitt's work on Cep
问题详情
The passage implies that Leavitt"s work on Cepheid variables would not have been possible without the availability of______ .
A．the camera as a scientific tool
B．techniques for determining the distances between stars
C．a method of measuring a star"s gravitational force
D．an understanding of the chemical properties of stars此题为多项选择题。请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：A
解析：本题的四个选项中，只有A项为正确答案。这可从文中第二段的最后一句“This variation in brightness could be recorded and precisely measured with the help of the camera，then still a new tool in astronomy”推知，即没有摄像机就不可能准确地记录和测量亮度的变化。
