Natural rubber is a polymer of .......

Which initiator is used for the free radical addition polymerization process?

Alkyd resins are condensation polymers formed by the reaction of a dibasic acid and . . . . . . .

Ziegler-Natta catalyst is used in the manufacture of

The catalyst used for the polymerisation of olefins is

The correct functional group $X$ and the reagent/reaction conditions $Y$ in the following scheme are:
$X-(CH_2)_4-X \xrightarrow{Y} \text{condensation polymer}$
$(i) \text{ with } HOOC-(CH_2)_4-COOH / \text{heat}$
$(A) X = COOCH_3, Y = H_2 / Ni / \text{heat}$
$(B) X = CONH_2, Y = H_2 / Ni / \text{heat}$
$(C) X = CONH_2, Y = Br_2 / NaOH$
$(D) X = CN, Y = H_2 / Ni / \text{heat}$