The spectrum of hydrogen atom consists of different series, each corresponding to transitions of electrons between energy levels. The four main series are:
1. Lyman series: Transitions to \( n = 1 \) from higher levels. This series lies in the ultraviolet region.
2. Balmer series: Transitions to \( n = 2 \) from higher levels. This series lies in the visible region.
3. Paschen series: Transitions to \( n = 3 \) from higher levels. This series lies in the infrared region.
4. Brackett series: Transitions to \( n = 4 \) from higher levels. This series also lies in the infrared region.
5. Pfund series: Transitions to \( n = 5 \) from higher levels. This series lies in the far infrared region.
Thus, the Lyman series is the series that lies in the ultraviolet region. Therefore, the correct answer is (D).