These spectra are from the same element. Which is an emission spectrum, which an absorption spectrum? A. Either could be emission (or absorption), depending on the conditions with which they were made.
B. Top is absorption; bottom emission.
C. Can't tell without knowing the element.
D. Top is emission; bottom absorption.

D. Top is emission; bottom absorption.

Explanation:

Emission and spectrum of elements are due to the element absorbing or emitting wavelength of e-m energy. Elementary particles of elements can absorb energy from a ground state to enter an excited state, creating an absorption spectrum, or they can lose energy and fall back to a lower energy state, creating an emission spectrum. A simple rule to differentiate between an emission and an absorption spectrum is that: "all absorbed wavelength is emitted, but not all emitted wavelength is absorbed."

From the image, the lines indicates wavelengths. We can see that all of the wavelengths of the bottom absorption spectrum coincides with some of the wavelength of the upper emission wavelengths.

d) the number of neutrons plus the number of protons