How proteins are made​

Proteins are an important class of molecules that carry out most of the work inside cells. The building blocks of proteins are smaller organic molecules called amino acids. Most organisms, including humans, use only 20 different amino acids to assemble the vast multitude of proteins needed to build and run a cell.

To build proteins, cells use a complex assembly of molecules called a ribosome. The ribosome assembles amino acids into the proper order and links them together via peptide bonds. This process, known as translation, creates a long string of amino acids called a polypeptide chain.  

After the polypeptide chain is synthesized, it will sometimes undergo additional processing. For example, some proteins will have certain amino acids removed. Or extra molecules such as sugars or phosphates may be attached to some of the amino acids in a protein.

proteins are made of large numbers of amino acids joined end to end. The chains fold up to form 3d molecules with complex shapes - you could think of it as origami with very long and thin piece of paper

i believe the correct answer is d

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.