Red phosphorus is used in the manufacture of safety matches. This is due to the fact that A. it show phosphorescence B. at ordinary temperature, it is less reactive than other varieties of phosphorus C. it cannot be converted to white phosphorus on heating D. it does not react with halogen on heating

The correct answer is: B. at ordinary temperature, it is less reactive than other varieties of phosphorus.

Red phosphorus is a less reactive form of phosphorus than white phosphorus. It is used in the manufacture of safety matches because it is less likely to ignite spontaneously than white phosphorus. White phosphorus is highly flammable and can ignite when exposed to heat, friction, or light. Red phosphorus is also less toxic than white phosphorus.

Option A is incorrect because red phosphorus does not show phosphorescence. Phosphorescence is the emission of light after exposure to light. Red phosphorus does not emit light after exposure to light.

Option C is incorrect because red phosphorus can be converted to white phosphorus on heating. Red phosphorus is converted to white phosphorus when it is heated to a temperature of 250 degrees Celsius.

Option D is incorrect because red phosphorus does react with halogen on heating. Red phosphorus reacts with halogens to form phosphorus halides.