A

Step 1: Understanding the types of spectra:
- A continuous spectrum displays all the colors of light without any gaps and is produced by solid, liquid, or densely packed gases.
- A line spectrum consists of distinct lines representing specific wavelengths and is typically emitted by gases when they are excited.
- A band spectrum includes a series of closely spaced lines or bands and is produced by larger molecules.
- An absorption spectrum shows dark lines or bands against a continuous spectrum, indicating the absorption of specific wavelengths by a substance.

Step 2: Analyzing the emission from a glowing solid:
A glowing solid emits light through thermal radiation, which results in a continuous spectrum spanning all visible wavelengths.

Conclusion: Since the question specifies a glowing solid, the correct type of spectrum emitted is a continuous spectrum.
Therefore, the correct answer is A.