<span>Changing one amino acid in the protein hemoglobin causes sickle-cell anemia.</span>
<span>a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.</span>
Crocodiles belong to Reptiles. Reptiles are <span>a cold-blooded vertebrates. </span>
Answer: oxygen
Explanation: It is oxygen because we always need oxygen for many things and organisms
