Aprotein containing more than one polypeptide chain exhibits the level of protein structure.
a) primary
b) secondaryc) tertiaryd) quaternary
e) infinite
d) 3.14 factual recall42

the correct option is D.

Explanation:

in case of quaternary level of protein structure , protein has more than one polypeptide chains  and in this level , the polypeptide chains are aggregated and held together by hydrophobic interactions, hydrogen and ionic bonds. this specific arrangement is called the quaternary structure.for example :-

Haemoglobin the oxygen carrying protein of red blood cells, exhibits such a structure.

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.

answer; ///(b) it is composed of four protein chains and four heme groups;