A food chain starts with

Concept: Photosynthesis is the initiator of the food chain as the food and energy produced by plants are consumed by consumers. 

Green plants are called autotrophs. They prepare their own food by the process of photosynthesis in the presence of sunlight and with the pigment known as chlorophyll. The process in which they absorb carbon dioxide from air and water from the soil and release oxygen to prepare food is called photosynthesis.

Hence, the correct answer is option B.