Electron poor species are stabilized by neighboring atoms that can donate electron density. The most common way to interpret rich neighbors here is the observation that increasing the number of alkyl groups on the carbon bearing the free radical increases its stability. 

BUNA-N is formed by removal of water molecule so it is condensation polymer.

A radical initiator is a species that acts as the reactant of the initiation step of a radical chain reaction but does not participate in any of the propagation steps.
Radical initiators are substances that can produce radical species under mild conditions and promote radical reaction. These substances generally possess weak bonds that have small bond dissociation energy. Radical initiators are utilized in industrial processes such as polymer synthesis. Typical examples are halogen molecules, azo compounds and organic and inorganic peroxides such as Benzoyl peroxide, di- t-Butyl peroxide.

The polymers polyethene (PE), low density polyethene(LDPE), high density polyethene(HDPE) and teflon (polytetrafluoroethylene) can be made by free radical addition polymerisation (also known as chain growth polymerisation) mechanism.  To obtain free radicals, initiators such as benzoyl peroxide, tert-butyl peroxide or acetyl peroxide are used.

$\begin{bmatrix}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-\end{bmatrix} _n$ 

Glyptal is not a polyamide. It is an alkyd resin obtained from polyhydric alcohols and polybasic organic acids or their anhydrides; used for surface coatings .

ELASTOMER  -  $Elastomers$ are rubber-like solids with elastic properties.
FIBRE  -  Fibre polymers are the thread forming solids with high tensile strength and high modulus.
THERMOSETTING  POLYMER  - These polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross-linking in moulds and again become infusible.
POLYSTYRENE - $Polystyrene$ is a thermoplastic polymer. It is formed by cation polymerisation. Hence, it is an example of a $cation$ $polymerisation$ $polymer$.

Polylactic acid is a thermoplastic aliphatic polyester derived from renewable resources
Polylactic acid is used for post operative stitches as it breaks down inside the body within $6$ months to $2$ years.

Polychloroethene is an addition polymer. Chloroethene can polymerise to form poly(chloroethene). Hence they can be cracked to produce chlorinated alkenes.

Styrene, also known as ethenylbenzene is an organic compound with molecular formula $C _6H _5CH=CH _2$

HDPE (high-density polyethene) and LDPE (low-density polyethene) polymerize by Ziegler-Natta Catalytic Polymerization reaction. 

$\text{reactivity is proportional to tendecy of donating electron by braking double bonds.}$

The full form of PVC is Polyvinyl chloride. It is polymer of vinyl chloride.
$ \displaystyle  \underset {  \displaystyle  \text {vinyl chloride } }{   nCH _2=   \underset {   \underset {\displaystyle Cl}{|}  }{C} H} \xrightarrow { \text { polymerisation }}    \underset {  \displaystyle  \text { Polyvinyl chloride
} }{   (-CH _2-   \underset {   \underset {\displaystyle Cl}{|}  }{C} H -) _n}$

The full form of PVC is Polyvinyl chloride. It is polymer of vinyl chloride.
$ \displaystyle  \underset {  \displaystyle  \text {vinyl chloride } }{   nCH _2=   \underset {   \underset {\displaystyle Cl}{|}  }{C} H} \xrightarrow { \text { polymerisation }}    \underset {  \displaystyle  \text { Polyvinyl chloride
} }{   (-CH _2-   \underset {   \underset {\displaystyle Cl}{|}  }{C} H -) _n}$

With some additives in PVC, the physical and mechanical properties are improved.

PVC (polyvinyl chloride) is thermoplastic polymer. Its properties are between elastomers and fibers. On heating, it becomes soft and on cooling, become hard. It can be remoulded and recycled.

$\text{Double bonds breaks of one monomer for addition with another monomer.}$

$F _2C=CF _2$ is a monomer of polytetrafluoroethylene also called as Teflon.

Many common addition polymer are formed from unsaturated monomers having $C=C$ bond.

Condensation polymers involves monomers which join together losing a small molecules as byproducts such as $H _2O$, methanol, etc.

Polymer formation from monomers starts by condensation reaction between monomers by removal of small molecules.

Synthetic polymers are classified on the basis of their origin and are known as man-made polymers.

They are made from PVC (or polyvinylchloride) because they are hard and non-breakable.

Anionic addition polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization of vinyl monomers with strong electronegative groups. This polymerization is carried out through a carbanion active species. 

Solution:- (C) Formaldehyde

In cationic polymerization the most stable cation will show the highest reactivity.

The order of reactivity will be-

$CH _2 = CH-C _6H _5 > CH _2  = CHCH _3 > CH _2 = CHCl >CH _2 = CHCOOCH _3$

Option C is correct.