Answer:
The correct option is 'a': All the answers are correct.
Step-by-step explanation:
Since plant's are abundant and can manufacture their own food hence they serve as the beginning of all the food chains hence option 'b' is correct.
In the process of photosynthesis the plants make use of carbon dioxide, sunlight , water, in presence of a pigment called chlorophyll present in plant cells in organelles called as plastids to yield glucose which is a carbohydrate or simplest sugar and release oxygen into the atmosphere. Hence options 'c' and 'd' are also correct.