Final answer:
Isotactic and syndiotactic polypropene both have crystalline regions due to their regular patterns which allow close packing of chains, whereas atactic polypropene is more amorphous.
Step-by-step explanation:
The structural forms of polypropene that have crystalline regions are isotactic polypropene and syndiotactic polypropene. Isotactic polypropene has a regular pattern where all methyl groups are positioned on the same side of the polymer chain, which facilitates crystalline structure formation due to the regularity and ability of chains to pack closely together. Syndiotactic polypropene, on the other hand, has alternating positions of the methyl groups on the polymer chain, which also allows for a level of order that can form crystalline sections. Atactic polypropene has randomly positioned methyl groups, which leads to a more amorphous structure with less potential for crystalline regions. Therefore, the answer to the student's question is option d) Both b and c.