The answer is A, because the phytoplankton is the foundation of this food web. Without your foundation, "the building will begin to crumble".
        
                    
             
        
        
        
Answer: Sunlight
Explanation: Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.
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They are all tetrapoda.
Tetrapods are animals (group of vertebrates) with four limbs including amphibians (frogs), reptiles (caimans), birds (parrots) and mammals (hares, humans). Even though the subgroups within Tetrapods differ a lot, they all have various adaptations of the skeleton and muscles that enable them movement on land, adaptations of cranium (for head stability), tissues that reduce water loss (because of living outside the water)…Except amphibians all other tetrapoda are amniotes (have amnion layer around embryo)