How Can Amino Acids in a Protein Be Any Closer

How can amino acids in a protein be any closer to one another than their spaced positions in the linear string?

A) Many amino acids break their covalent bonds in the linear arrangement and form closer ionic bonding arrangements.
B) Amino acids in their linear primary structure are constantly breaking and reforming their covalent bonds. When they are not in a bonding arrangement, they can be closer to adjacent amino acids temporarily.
C) As amino acid chains fold into their tertiary structure, this commonly brings some amino acids closer together than their linear spaced positions.
D) Amino acids only form covalent bonds with one another and do not associate with one another at a distance closer than the covalent bond.