In Measurements Made with Spectroscopes, Why Is the Light First

Multiple Choice

In measurements made with spectroscopes, why is the light first sent through a narrow slit?

A) to increase the interference effects
B) to produce broad-- i.e., wide-- spectral lines on the screen
C) to increase the bending effect by the prism
D) to produce narrow spectral lines on the screen
E) to increase the amount of light hitting the prism.