What maintains the secondary structure of a protein?
select one:
a. hydrogen bonds between the amino group of one peptide bond and the carboxyl group of another peptide bond
b. peptide bonds between adjacent amino acids
c. hydrogen bonds between the carboxyl group of one peptide bond and the r group of another amino acid incorrect
d. disulfide bonds between the amino group of one peptide bond and the r group of another amino acid

The correct answer is a. hydrogen bonds between the amino group of one peptide bond and the carboxyl group of another peptide bond.

Explanation:

The secondary structure of proteins are formed by α-helices and β-structures, that can be supported by hydrogen bonds between amine hydrogens and another peptide bond.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .