For each of the following pairs of polymers, plot and label schematic stress–strain curves on the same graph [i. e., make separate plots for parts (a) to (c)].

(a) polyisoprene having a number-average molecular weight of 100,000 g/mol and 10% of available sites crosslinked; polyisoprene having a number-average molecular weight of 100,000 g/mol and 20% of available sites crosslinked

(b) syndiotactic polypropylene having a weight-average molecular weight of 100,000 g/mol; atactic polypropylene having a weight-average molecular weight of 75,000 g/mol

(c) branched polyethylene having a number-average molecular weight of 90,000 g/mol; heavily crosslinked polyethylene having a number-average molecular weight of 90,000 g/mol

i have the answer, i am looking for an explanation.