At what point in the light-capturing reactions is the electromagnetic energy of light converted into chemical energy? where does this occur?

The conversion of light energy to chemical energy first occurs when electrons are transferred from excited photopigments to an electron carrier in a photosystem (pigments together with proteins organized into complexes and located in the thylakoid membranes of chloroplasts).

The light-dependent reactions is one of the two successive phases that occur during photosynthesis (other is light-independent reactions). The light-dependent reactions use sunlight energy (electromagnetic radiation) to make the energy storage molecule ATP and the reduced electron carrier NADPH. In the light-independent reactions (also called Calvin cycle), CO2 is absorbed and fixed in order to build three-carbon sugars (glyceraldehyde-3-phosphate) and this process is fueled by, ATP and NADPH from the light reactions.

the answer to your question is:

c. complementary base-pairing

it's c. (to reduce the greenhouse effect/carbon gasses)