When a high voltage is applied to a low-pressure gas causing it to glow, it will generate which type of spectrum

Line emission.

Explanation:

According to Isaac Newton, he postulated that light consists of little (tiny) particles which typically travels in a straight line and from his experimental investigation he observed that white light comprises of a mixture of colors.

Sir Newton observed that, when light shines on a piece of metal, the metal releases electrons because the energy of the tiny light particles are greater than the binding energy of the electrons residing in the metal. This theory is known as the particle model of light.

A line emission would appear in a spectrum when specific wavelength is being emitted by the source of light.

When a high voltage is applied to a low-pressure gas causing it to glow, it will generate line emission.

For example, if a sample of hydrogen gas at low-pressure undergoes or experiences a high voltage electrical discharge, the isolated hydrogen gas would generate a red light (line emission).

i think the answer is a, hope this is right, that would be my best guess.