The correct option is
B Photosynthesis
Green plants are known as autotrophs. They prepare their own food in the presence of sunlight, with the help of a pigment called chlorophyll. The process, in which they take away carbon dioxide from air and water from the soil and give out oxygen to prepare food is called photosynthesis.
So we can say the process of photosynthesis is the initiator of food chain as the food and energy produced by plants is consumed further by consumers.
So, option C "Photosynthesis" is the correct option.