Explanation:
The hydrogen spectrum consists of a series of lines corresponding to the transitions of electrons between different energy levels in the hydrogen atom. Each series of lines is characterized by a particular set of transitions, and each series has its own upper and lower limits in wavelength.

The different series of the hydrogen spectrum are named after the scientist who first described them, and they are:

1. Lyman series: This series has its lower limit at the ultraviolet end of the spectrum (at 91.2 nm), and it corresponds to transitions from higher energy levels to the ground state (n=1).

2. Balmer series: This series has its lower limit in the visible region of the spectrum (at 364.6 nm), and it corresponds to transitions from higher energy levels to the first excited state (n=2).

3. Paschen series: This series has its lower limit in the infrared region of the spectrum (at 820.1 nm), and it corresponds to transitions from higher energy levels to the second excited state (n=3).

4. Brackett series: This series has its lower limit in the infrared region of the spectrum (at 1458 nm), and it corresponds to transitions from higher energy levels to the third excited state (n=4).

5. Pfund series: This series has its lower limit in the infrared region of the spectrum (at 2278 nm), and it corresponds to transitions from higher energy levels to the fourth excited state (n=5).

The upper limit of each series is determined by the energy of the highest level involved in the transitions. For example, the upper limit of the Balmer series is determined by the energy of the third excited state (n=4), which is lower than the energy of the fourth excited state (n=5) that is involved in the Pfund series.

In this question, the upper limit of the wavelength is given as 18752, which corresponds to the Paschen series. Therefore, the correct answer is option C.