单项选择题

What is one reason astronomers make long-time exposures

A．To spend less time at their telescopes.
B．To overcome the problem of weak light.
C．To take more photographs.
D．To photograph astronomical objects without using a telescop

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单项选择题

According to the speaker, what do people often think about astronomers

A．They spend most of their time looking through telescopes.
B．They are constantly analyzing data.
C．They often live near observatories.
D．They devote a lot of time to theoretical problems.

单项选择题

Why do astronomers often use photographic plates

A．To decrease the time it takes to photograph objects.
B．To avoid using a telescope.
C．To sharpen the color of what they observe.
D．To obtain images of distant objects.