Question

How do astronomers know which element is present where?

A. By looking for specific wavelengths of light that each element produces
B. By comparing the density of the gas to the densities of various elements
C. By measuring the temperature of each part of the gas
D. By observing chemical reactions taking place in the nebula​

Answer 1

A. by looking for specific wavelengths of light that each element produces

Step-by-step explanation:

Astronomers tend to use a spectroscope that helps find light and wavelengths.