In atomic absorption spectroscopy, the mechanism of light absorption is

A、 Selective absorption of light during molecular vibration and rotation energy level transitions
B、The absorption when the ground state atom absorbs the characteristic radiation and transitions to the excited state and then returns to the ground state
C、The absorption caused by the molecular electrons absorbing the characteristic radiation and then transitions to the excited state
D、Absorption caused by transition to excited state after ground state atom absorbs the characteristic radiation