An atomic emission spectrum is understood as a succession of linear formed when light passes through a prism. Said prism is responsible for separating it in each of the light frequencies of which it is composed. I enclose an image that shows what the atomic emission spectrum of hydrogen is like.
There it can be seen that when the light of a hydrogen gas discharge tube crosses a prism, it is divided into 4 linear. These lines correspond to a different electronic transition from a higher energy state to a lower energy state. Therefore the correct answer is B.
The lines in an atomic line emission spectrum are due to the movement of electrons from higher energy states to lower energy states in atoms.
