When is the absorption spectrum of an electron generated
a. when an electron in an atom is excited to a higher energy state
b. when an electron in an atom is in the excited state
c. when an electron in an atom returns from an excited state to a lower energy state
d. when an electron in an atom is in the ground state

A. when an electron in an atom is excited to a higher energy state

Explanation:

An absorption spectrum consists of dark lines on a visible background. The dark lines indicate the wavelength which is absorbed by the electron to jump from lower energy state to higher energy state.

Electron requires energy to jump to higher state. Specific wavelength is absorbed by the electron which appears as dark line. This wavelength is equivalent to energy difference between the two levels the electron is jumping.