The overall process that uptakes energy-poor molecules (CO2 and H2O) from their reservoirs in nature and converts them into energy-rich molecules is

Photosynthesis

Explanation:

Photosynthesis is a process by  which photosynthetic organisms use the energy of captured sunlight to convert energy-poor molecules such as carbon (iv), CO₂ and water (H₂O) into energy-rich organic molecules sch as carbohydrates e.g. glucose.

Photosynthesis occurs in a variety of bacteria  and algae as well in vascular plants. The overall equation for the reaction of photosynthesis is as follows:

CO₂ + H₂O + light>  (CH₂O) + O₂

It is a redox reaction in which  water donates electrons (as hydrogen) for the reduction of  CO₂ to carbohydrate, (CH₂O).

Carbohydrates are energy-rich molecules which serves as energy sources for many living organisms.

i'm pretty sure its b i might be wrong though!