What is the mechanism of uncatalyzed photo-initiation of polymerization, when light of specific wavelength falls on monomer?

• A. monomer directly decomposes to give radicals
• B. monomer generates excites species by absorbing light quanta and then decompose into radicals by homolysis
• C. photo-initiator is added to monomer and decomposes to radicals by photolysis
• D. all of the mentioned