The initiator at low temperature is option IV. Option D
Even at low temperatures, unsaturated compounds, which have double or triple bonds between carbon atoms, can occasionally function as initiators in specific chemical reactions, especially radical reactions. This is due to the fact that unsaturation creates a space where chemical reactions can occur and produce reactive intermediates.
For instance, in radical reactions, homolytic cleavage and other processes can result in the formation of radicals when a double bond is present. With their unpaired electrons, radicals are extremely reactive organisms that have the ability to start and spread radical chain reactions.