Which of the following is a natural polymer? Buna – S, protein, PVC

Hint:Natural polymers are polymers that are obtained naturally and generally they are non toxic in nature. They naturally occur means they are made by animals, plants, fungi, etc.

Complete step-by-step answer:Polymers - Polymer is defined as very large molecules having high molecular mass (103-107u). The process of formation of polymer is known as polymerization, in this process the joining of repeated structural units combined together in large scale to form a polymer. For example formation of polythene by combining ethane monomers.
Some common classification of polymer is following: -
1.Natural polymers
2.Semi – synthetic polymers
3.Synthetic polymers
Proteins are the polymers which naturally occur in nature that means they are made by living beings like animals, plants etc. thus they are termed as Natural polymers. Some other examples of natural polymers are cellulose, wool, silk, starch, natural rubber, cellulose, starch, some resins, DNA etc.
The remaining two polymers namely, Buna-S and PVC are human-made polymers i.e. they are synthetic polymers.

Additional information: Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Natural polymers are widely occurring in nature or are extracted from plants or animals. Natural polymers are essential to daily life as our human forms are based on them.
Advantages of proteins are:
-Readily and abundantly available
-Nontoxic products
-Comparatively less expensive
-Can be modified to get semi synthetic polymer forms

Note: When talking about natural or artificial polymers we must always keep in mind the fact that the terminologies are just a representation of the source of origin of the polymer from where it was first discovered and does not mean that they cannot be obtained from any other source.