The correct answer is A. Temperature.
The amount and type of radiation emitted by an object depends on its temperature. The hotter an object is, the more radiation it emits, and the shorter the wavelength of that radiation. This is why objects that are very hot, such as the sun, emit visible light, while objects that are cooler, such as a campfire, emit infrared radiation.
Thermal conductivity is a measure of how easily heat can flow through a material. Density is a measure of how much mass is contained in a given volume. Latent heat is the heat that is absorbed or released when a substance changes its state, such as from solid to liquid or liquid to gas.
While these properties can affect the amount of radiation that an object emits, they are not the primary factors. The temperature of an object is the most important factor in determining the amount and type of radiation that it emits.