(a)Polypropene has chiral`C`atoms and,therefore,exists in different forms as mentioned .Polyethylidene chloride,on the other hand ,does not have chiral`C` atom and thus does not exist in the forms mentioned.
(b)All formsof polypropence`(PP)`would exist in equal amount of enantiomers,with net specific rotaiton of zero,So each form would exist as racemates.