What is the expression for rate of initiation in catalyzed photo-polymerization? ( I0 and φ are the intensity of incident light and number of pairs of chain radicals formed per quantum of light absorbed, respectively and ε be the molar absorption coefficient )

• A. 2φεI0[I] 
• B. φεI0[M] 
• C. 2φεI0[M] 
• D. φεI0[I]