1. which of the following statements about proteins is incorrect?

(a) all proteins are made up of some combination of 20 essential amino acids.
(b) like nucleic acids, polypeptides have polarity.
(c) a single polypeptide has primary, secondary and tertiary structures.
(d) α-helix and β-pleated sheets do not require specific sequence of amino acids to form.
(e) some proteins contain more than one polypeptide chain.

The diagram below shows the layers of a rock having a trilobite: a rock column labeled rock is shown. the column has three layers. the bottommost layer of the rock has one shaded rhomboid shape, the middle layer has a rhombus with a diagonal along with two identical organisms marked as, trilobite, in the key, the top layer has two semicircles. a key is shown on the right side of the diagram. the shaded rhombus is marked as a, the rhombus with the diagonal is marked as b, the semicircle is marked as c which statement about the rock fossils is true?