Answer:
The correct answer is (3) synthesize nutrients using carbon dioxide and water.
Explanation:
Autotrophs are those organisms that are able to make their own food. Most of the autotrophs are plants and algae which synthesize their food in the form of carbohydrate like glucose by using carbon dioxide and glucose as precursor.
Energy is required by the autotrophs to make food which is provided by the solar radiation which is absorbed by a pigment called chlorophyll present chloroplast of plants.
These autotrophs are primary producers which are then consumed by heterotrophs that can not make their own food. Therefore only autotrophs synthesize nutrients using CO₂ and H₂O so the right answer is third.
