Answer the following question given this paragraph: 

PET is used in tires, photographic film, food packaging, and clothing. Polyester fabric is used in permanent-press clothing. Its resistance to wrinkling comes from the cross-linking of the polymer strands.


Q: Polyester fabric's resistance to wrinkling comes from the cross-linking of what?

 Choices:

- algae strands

- velocity strands

- wool strands

- polymer strands

A:
polymer strands
