The bright-line spectra observed for different elements results from:
a. collisions between electrons at different energies.
b. electrons jumping to a higher energy level
c. electrons moving to a lower energy level

Hello teatea,

The correct answer is (c)

"...it is electron transitions (movements between higher and lower
energy levels) that produces both bright line (emission) spectra and
dark line (absorption) spectra. The bright line (emission) spectra are
produced when an excited electron (one which has absorbed energy)
tumbles back down to its original stable location (its ground state)
with respect to the nucleus."
From: NASA Educational Brief Subject: Spectroscopy; Topic: Identifying
Elements In The Stars
http://edmall.gsfc.nasa.gov/99invest.Site/science-briefs/ace/ed-spectro.html

Search strategy on Google: "line spectra" elements